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Page No 152:
Question 1:
Answer:
(i) 24:56 = 24 = 24 â÷ 8 = 3
56 56 â÷ 8 7
As the H.C.F. of 3 and 7 is 1, the simplest form of 24:56 is 3:7.
(ii) 84 paise to Rs 3 = Rs 0.84 to R. 3 = 0.84 = 0.84â ÷ 3 = 0.28 = 28 = 28 â÷ 4 = 7
3 3 â÷ 3 1 100 100 â÷ 4 25
As the H.C.F. of 7 and 25 is 1, the simplest form of 0.84:3 is 7:25.
(iii) 4 kg:750 g = 4000 g:750 g = 4000 â÷ 250 = 16
750 â÷ 250 3
As the H.C.F. of 16 and 3 is 1, the simplest form of 4000:750 is 16:3.
(iv) 1.8 kg:6 kg = 1.8 = 18 = 18 â÷ 6 = 3
6 60 60 â÷ 6 10
As the H.C.F. of 3 and 10 is 1, the simplest form of 1.8:6 is 3:1.
(v) 48 minutes to 1 hour = 48 minutes to 60 minutes = 48:60 = 48 â÷ 12 = 4
60 â÷ 12 5
As the H.C.F. of 4 and 5 is 1, the simplest form of 48:60 is 4:5.
(vi) 2.4 km to 900 m = 2400m:900m = 2400 = 24 = 24 â÷ 3 = 8
900 9 9 â÷ 3 3
As the H.C.F. of 8 and 3 is 1, the simplest form of 2400:900 is 8:3.
Page No 152:
Question 2:
(i) 24:56 = 24 = 24 â÷ 8 = 3
56 56 â÷ 8 7
As the H.C.F. of 3 and 7 is 1, the simplest form of 24:56 is 3:7.
(ii) 84 paise to Rs 3 = Rs 0.84 to R. 3 = 0.84 = 0.84â ÷ 3 = 0.28 = 28 = 28 â÷ 4 = 7
3 3 â÷ 3 1 100 100 â÷ 4 25
As the H.C.F. of 7 and 25 is 1, the simplest form of 0.84:3 is 7:25.
(iii) 4 kg:750 g = 4000 g:750 g = 4000 â÷ 250 = 16
750 â÷ 250 3
As the H.C.F. of 16 and 3 is 1, the simplest form of 4000:750 is 16:3.
(iv) 1.8 kg:6 kg = 1.8 = 18 = 18 â÷ 6 = 3
6 60 60 â÷ 6 10
As the H.C.F. of 3 and 10 is 1, the simplest form of 1.8:6 is 3:1.
(v) 48 minutes to 1 hour = 48 minutes to 60 minutes = 48:60 = 48 â÷ 12 = 4
60 â÷ 12 5
As the H.C.F. of 4 and 5 is 1, the simplest form of 48:60 is 4:5.
(vi) 2.4 km to 900 m = 2400m:900m = 2400 = 24 = 24 â÷ 3 = 8
900 9 9 â÷ 3 3
As the H.C.F. of 8 and 3 is 1, the simplest form of 2400:900 is 8:3.
Answer:
(i) 36:90 = 36 = 36 â÷ 18 = 2 (As the H.C.F. of 36 and 90 is 18.)
90 90 â÷ 18 5
Since the H.C.F. of 2 and 5 is 1, the simplest form of 36:90 is 2:5.
(ii) 324:144 = 324 = 324 â÷ 36 = 9 (As the H.C.F. of 324 and 144 is 36.)
144 144 â÷ 36 4
Since the H.C.F. of 9 and 4 is 1, the simplest form of 324:144 is 9:4.
(iii) 85:561 = 85 = 85 â÷ 17 = 5 (As the H.C.F. of 85 and 561 is 17.)
561 561 ââ÷ 17 33
Since the H.C.F. of 5 and 33 is 1, the simplest form of 85:561 is 5:33.
(iv) 480:384 = 480 = 480 â÷ 96 = 5 (As the H.C.F. of 480 and 384 is 96.)
384 384 ââ÷ 96 4
Since the H.C.F. of 5 and 4 is 1, the simplest form of 480:384 is 5:4.
(v) 186:403 = 186 = 186 ÷ 31 = 6 (As the H.C.F. of 186 and 403 is 31.)
403 403 ÷ 31 13
Since the H.C.F. of 6 and 13 is 1, the simplest form of 186:403 is 6:13.
(vi) 777:1147 = 777 â÷ 37 = 21 (As the H.C.F. of 777 and 1147 is 37.)
1147 â÷ 37 31
Since the H.C.F. of 21 and 31 is 1, the simplest form of 777:1147 is 21:31.
Page No 152:
Question 3:
(i) 36:90 = 36 = 36 â÷ 18 = 2 (As the H.C.F. of 36 and 90 is 18.)
90 90 â÷ 18 5
Since the H.C.F. of 2 and 5 is 1, the simplest form of 36:90 is 2:5.
(ii) 324:144 = 324 = 324 â÷ 36 = 9 (As the H.C.F. of 324 and 144 is 36.)
144 144 â÷ 36 4
Since the H.C.F. of 9 and 4 is 1, the simplest form of 324:144 is 9:4.
(iii) 85:561 = 85 = 85 â÷ 17 = 5 (As the H.C.F. of 85 and 561 is 17.)
561 561 ââ÷ 17 33
Since the H.C.F. of 5 and 33 is 1, the simplest form of 85:561 is 5:33.
(iv) 480:384 = 480 = 480 â÷ 96 = 5 (As the H.C.F. of 480 and 384 is 96.)
384 384 ââ÷ 96 4
Since the H.C.F. of 5 and 4 is 1, the simplest form of 480:384 is 5:4.
(v) 186:403 = 186 = 186 ÷ 31 = 6 (As the H.C.F. of 186 and 403 is 31.)
403 403 ÷ 31 13
Since the H.C.F. of 6 and 13 is 1, the simplest form of 186:403 is 6:13.
(vi) 777:1147 = 777 â÷ 37 = 21 (As the H.C.F. of 777 and 1147 is 37.)
1147 â÷ 37 31
Since the H.C.F. of 21 and 31 is 1, the simplest form of 777:1147 is 21:31.
Answer:
(i) Rs 6.30:Rs 16.80
6.30 = 63 = 63 â÷ 21 = 3 (H.C.F. of 63 and 168 is 21.)
16.80 168 168 â÷ 21 8
Ratio = 3 : 8
(ii)3 weeks:30 days = 21days:30 days (1 week = 7 days)
21 = 21 â÷ 3 = 7 (H.C.F. of 21 and 30 is 3.)
30 30 â â÷ 3 10
Ratio = 7 : 10
(iii) 3 m 5 cm:35 cm = 305 cm:35 cm (1 m = 100 cm)
305 = 305 â÷ 5 = 61 (H.C.F. of 305 and 35 is 5.)
35 35 â÷ 5 7
Ratio = 61:7
(iv) 48 min:2 hours 40 min = 48 min:160 min (1 hour = 60 mins)
48 = 48 â÷ 16 = 3 (H.C.F. of 48 and 160 is 16.)
160 160 â÷ 16 10
Ratio = 3:10
(v) 1 L 35 mL:270 mL = 1035 mL:270 mL (1 L = 1000 mL)
1035 = 1035 â÷ 45 = 23 (H.C.F. of 1035 and 270 is 45.)
270 270 â÷ 45 6
Ratio = 23:6
(vi) 4 kg:2 kg 500 g = 4000 g:2500 g (1 kg= 1000 g)
4000 = 40 = 40 â÷ 5 = 8 (H.C.F. of 40 and 25 is 5.)
2500 25 25 â÷ 5 5
Ratio = 8:5
Page No 152:
Question 4:
(i) Rs 6.30:Rs 16.80
6.30 = 63 = 63 â÷ 21 = 3 (H.C.F. of 63 and 168 is 21.)
16.80 168 168 â÷ 21 8
Ratio = 3 : 8
(ii)3 weeks:30 days = 21days:30 days (1 week = 7 days)
21 = 21 â÷ 3 = 7 (H.C.F. of 21 and 30 is 3.)
30 30 â â÷ 3 10
Ratio = 7 : 10
(iii) 3 m 5 cm:35 cm = 305 cm:35 cm (1 m = 100 cm)
305 = 305 â÷ 5 = 61 (H.C.F. of 305 and 35 is 5.)
35 35 â÷ 5 7
Ratio = 61:7
(iv) 48 min:2 hours 40 min = 48 min:160 min (1 hour = 60 mins)
48 = 48 â÷ 16 = 3 (H.C.F. of 48 and 160 is 16.)
160 160 â÷ 16 10
Ratio = 3:10
(v) 1 L 35 mL:270 mL = 1035 mL:270 mL (1 L = 1000 mL)
1035 = 1035 â÷ 45 = 23 (H.C.F. of 1035 and 270 is 45.)
270 270 â÷ 45 6
Ratio = 23:6
(vi) 4 kg:2 kg 500 g = 4000 g:2500 g (1 kg= 1000 g)
4000 = 40 = 40 â÷ 5 = 8 (H.C.F. of 40 and 25 is 5.)
2500 25 25 â÷ 5 5
Ratio = 8:5
Answer:
Mr Sahai's earning = Rs 16800
Mrs Sahai's earning = Rs 10500
(i) Ratio = 16800:10500 = 168:105 = 168 â÷ 21 = 8 (H.C.F. of 168 and 105 is 21.)
105 â â÷ 21 5
Mr Sahai's income:Mrs Sahai's income = 8:5
(ii)Ratio = 10500:16800 = 105:168 = 105 â÷ 21 = 5 (H.C.F. of 168 and 105 is 21.)
168 â â÷ 21 8
Mrs Sahai's income:Mr Sahai's income = 5:8
(iii) Total income = 16800 + 10500 = Rs 27300
Ratio = 16800:27300 = 168:273 = 168 = 168 â÷ 21 = 8 (H.C.F. of 168 and 273 is 21.)
273 273 â÷ 21 13
Mrs Sahai's income:Total income = 8:13
Page No 152:
Question 5:
Mr Sahai's earning = Rs 16800
Mrs Sahai's earning = Rs 10500
(i) Ratio = 16800:10500 = 168:105 = 168 â÷ 21 = 8 (H.C.F. of 168 and 105 is 21.)
105 â â÷ 21 5
Mr Sahai's income:Mrs Sahai's income = 8:5
(ii)Ratio = 10500:16800 = 105:168 = 105 â÷ 21 = 5 (H.C.F. of 168 and 105 is 21.)
168 â â÷ 21 8
Mrs Sahai's income:Mr Sahai's income = 5:8
(iii) Total income = 16800 + 10500 = Rs 27300
Ratio = 16800:27300 = 168:273 = 168 = 168 â÷ 21 = 8 (H.C.F. of 168 and 273 is 21.)
273 273 â÷ 21 13
Mrs Sahai's income:Total income = 8:13
Answer:
Rohit's income = Rs 15300
Rohit's savings = Rs 1224
(i) Income:Savings = 15300:1224 = 15300 â÷ 612 = 25 (H.C.F. of 15300 and 1224 is 612.)
1224 â÷ 612 2
Income:Savings = 25:2
(ii) Monthly expenditure = Rs (15300 1224) = Rs 14076
Income:Expenditure = 15300:14076 = 15300 ÷ 612 = 25 (H.C.F. of 15300 and 14076 is 612.)
14076 â÷ 612 23
Income:Expenditure = 25:23
(iii) Expenditure : Savings = 14076:1224 = 14076 ÷ 612 = 23 (H.C.F. of 14076 and 1224 is 612.)
1224 â÷ 612 2
Expenditure:Savings = 23:2
Page No 152:
Question 6:
Rohit's income = Rs 15300
Rohit's savings = Rs 1224
(i) Income:Savings = 15300:1224 = 15300 â÷ 612 = 25 (H.C.F. of 15300 and 1224 is 612.)
1224 â÷ 612 2
Income:Savings = 25:2
(ii) Monthly expenditure = Rs (15300 1224) = Rs 14076
Income:Expenditure = 15300:14076 = 15300 ÷ 612 = 25 (H.C.F. of 15300 and 14076 is 612.)
14076 â÷ 612 23
Income:Expenditure = 25:23
(iii) Expenditure : Savings = 14076:1224 = 14076 ÷ 612 = 23 (H.C.F. of 14076 and 1224 is 612.)
1224 â÷ 612 2
Expenditure:Savings = 23:2
Answer:
Number of male:Number of female = 5:3
Let the number be x.
Number of male = 5x
âNumber of female = 3x
Number of male workers = 115
Now, 5x = 115
⇒ x = 115 = 23
5
Number of female workers in the mill = 3x = 3 × 23 = 69
Page No 152:
Question 7:
Number of male:Number of female = 5:3
Let the number be x.
Number of male = 5x
âNumber of female = 3x
Number of male workers = 115
Now, 5x = 115
⇒ x = 115 = 23
5
Number of female workers in the mill = 3x = 3 × 23 = 69
Answer:
Boys:Girls = 9:5
Let the number of boys = 9x
Let the number of girls = 5x
Total strength of the school = 448
According to given condition, we have:
9x + 5x = 448
⇒ 14x = 448
⇒ x = 448 = 32
14
Number of boys = 9x = 9 × 32 = 288
Number of girls = 5x = 5 â× 32 = 160
Page No 152:
Question 8:
Boys:Girls = 9:5
Let the number of boys = 9x
Let the number of girls = 5x
Total strength of the school = 448
According to given condition, we have:
9x + 5x = 448
⇒ 14x = 448
⇒ x = 448 = 32
14
Number of boys = 9x = 9 × 32 = 288
Number of girls = 5x = 5 â× 32 = 160
Answer:
Kamal:Madhu = 7:2
Sum of the ratio terms = 7 + 2 = 9
Kamal's share = 7 × 1575 = 11025 = Rs 1225
9 9
Madhu's share = 2 × 1575 = 3150 = Rs 350
9 9
Page No 152:
Question 9:
Kamal:Madhu = 7:2
Sum of the ratio terms = 7 + 2 = 9
Kamal's share = 7 × 1575 = 11025 = Rs 1225
9 9
Madhu's share = 2 × 1575 = 3150 = Rs 350
9 9
Answer:
A:B:C = 3:5:7
Sum of the ratio terms = 3 + 5 +7 = 15
A's share = 3 × 3450 = 10350 = Rs 690
15 15
B's share = 5 × 3450 = 17250 = Rs 1150
15 15
C's share = 7 × 3450 = 24150 = Rs 1610
15 15
Page No 152:
Question 10:
A:B:C = 3:5:7
Sum of the ratio terms = 3 + 5 +7 = 15
A's share = 3 × 3450 = 10350 = Rs 690
15 15
B's share = 5 × 3450 = 17250 = Rs 1150
15 15
C's share = 7 × 3450 = 24150 = Rs 1610
15 15
Answer:
Two number are in the ratio 11:12.
Let the numbers be 11x and 12x.
Given: 11x + 12x = 460
⇒ 23x = 460
⇒ x = 460 = 20
23
First number = 11x = 11 × 20 = 220
Second number = 12x = 12 × 20 = 240
Hence, the numbers are 220 and 240.
Page No 152:
Question 11:
Two number are in the ratio 11:12.
Let the numbers be 11x and 12x.
Given: 11x + 12x = 460
⇒ 23x = 460
⇒ x = 460 = 20
23
First number = 11x = 11 × 20 = 220
Second number = 12x = 12 × 20 = 240
Hence, the numbers are 220 and 240.
Answer:
Ratio of the two parts of line segment = 4:3
Sum of the ratio terms = 4 + 3 = 7
First part = 4 × 35 cm = 4 × 5 cm = 20 cm
7
Second part = 3 × 35 cm = 3 × 5 cm = 15 cm
7
Page No 152:
Question 12:
Ratio of the two parts of line segment = 4:3
Sum of the ratio terms = 4 + 3 = 7
First part = 4 × 35 cm = 4 × 5 cm = 20 cm
7
Second part = 3 × 35 cm = 3 × 5 cm = 15 cm
7
Answer:
Number of bulbs produced each day = 630
Out of 10 bulbs, 1 is defective.
Number of defective bulbs = 630 = 63
10
Number of defective bulbs produced each day = 63
Page No 152:
Question 13:
Number of bulbs produced each day = 630
Out of 10 bulbs, 1 is defective.
Number of defective bulbs = 630 = 63
10
Number of defective bulbs produced each day = 63
Answer:
Price of pencil = Rs 96 per score
Price of ball pen = Rs 50.40 per dozen
Price per unit of pencil = 96 = 4.8
20
Price per unit of ball pen = 50.40 = 4.2
12
Ratio = 4.8 = 48 = 48 â÷ 6 = 8
4.2 42 42 â÷ 6 7
Price of a pencil:Price of a ball pen = 8:7
Page No 152:
Question 14:
Price of pencil = Rs 96 per score
Price of ball pen = Rs 50.40 per dozen
Price per unit of pencil = 96 = 4.8
20
Price per unit of ball pen = 50.40 = 4.2
12
Ratio = 4.8 = 48 = 48 â÷ 6 = 8
4.2 42 42 â÷ 6 7
Price of a pencil:Price of a ball pen = 8:7
Answer:
Length:Width = 5:3
Let the length and the width of the field be 5x m and 3x m, respectively.
Width = 42 m
3x = 42
x = 42 = 14
3
Length = 5x = 5 × 14 = 70 metres
Page No 152:
Question 15:
Length:Width = 5:3
Let the length and the width of the field be 5x m and 3x m, respectively.
Width = 42 m
3x = 42
x = 42 = 14
3
Length = 5x = 5 × 14 = 70 metres
Answer:
Income:Savings = 11:2
Let the income and the saving be Rs 11x and Rs 2x, respectively.
Saving = Rs 1520
2x = 1520
x = 1520 = 760
2
Income = Rs 11x =Rs (11 × 760) = Rs 8360
Expenditure = Income Saving
= Rs (8360 1520 )
= Rs 6840
Page No 152:
Question 16:
Income:Savings = 11:2
Let the income and the saving be Rs 11x and Rs 2x, respectively.
Saving = Rs 1520
2x = 1520
x = 1520 = 760
2
Income = Rs 11x =Rs (11 × 760) = Rs 8360
Expenditure = Income Saving
= Rs (8360 1520 )
= Rs 6840
Answer:
Income:Expenditure = 7:6
Let the income and the expenditure be Rs 7x and Rs 6x, respectively.
Income = Rs 14000
7x = 14000
x = 14000 = 2000
7
Expenditure = Rs 6x = Rs 6 × 2000 = Rs 12000
Saving = Income Expenditure
= Rs (14000 12000)
= Rs 2000
Page No 152:
Question 17:
Income:Expenditure = 7:6
Let the income and the expenditure be Rs 7x and Rs 6x, respectively.
Income = Rs 14000
7x = 14000
x = 14000 = 2000
7
Expenditure = Rs 6x = Rs 6 × 2000 = Rs 12000
Saving = Income Expenditure
= Rs (14000 12000)
= Rs 2000
Answer:
Let the weight of zinc be x kg.
Ratio of zinc and copper = 7:9
Weight of copper in the alloy = 11.7 kg
7 = x
9 11.7
⇒ x = 11.7 × 7 = 81.9 = 9.1
9 9
Weight of zinc = 9.1 kg
Page No 152:
Question 18:
Let the weight of zinc be x kg.
Ratio of zinc and copper = 7:9
Weight of copper in the alloy = 11.7 kg
7 = x
9 11.7
⇒ x = 11.7 × 7 = 81.9 = 9.1
9 9
Weight of zinc = 9.1 kg
Answer:
A bus covers 128 km in 2 hours.
Speed of the bus = Distance = 128 km = 64 km/ hr
Time 2 hr
A train covers 240 km in 3 hours.
Speed of the train = Distance = 240 = 80 km /hr
Time 3
Ratio of their speeds = 64:80 = 64 = 64 ÷ 16 = 4
80 80 ÷ 16 5
Ratio of the speeds of the bus and the train = 4:5
Page No 153:
Question 19:
A bus covers 128 km in 2 hours.
Speed of the bus = Distance = 128 km = 64 km/ hr
Time 2 hr
A train covers 240 km in 3 hours.
Speed of the train = Distance = 240 = 80 km /hr
Time 3
Ratio of their speeds = 64:80 = 64 = 64 ÷ 16 = 4
80 80 ÷ 16 5
Ratio of the speeds of the bus and the train = 4:5
Answer:
(i) (3:4) or (9:16)
Making the denominator equal:
3 × 4 = 12 and 12 > 9
4 × 4 16 16 16
(3:4) > (9:16)
(ii) (5:12) or (17:30)
Making the denominator equal:
5 × 5 = 25 and 17 × 2 = 34
12 × 5 60 30 × 2 60
⇒ 25 < 34
60 60
(5:12) < (17:30)
(iii) (3:7) or (4:9)
Making the denominator equal:
3 × 9 = 27 and 4 × 7 = 28
7 × 9 63 9 â× 7 63
⇒ 27 < 28
63 63
(3:7) < (4:9)
(iv) (1:2) or (13:27)
Making the denominator equal:
1× 27 = 27 and 13 × 2 = 26
2 × 27 54 27 â× 2 54
⇒ 27 > 26
54 54
(1:2) > (13:27)
Page No 153:
Question 20:
(i) (3:4) or (9:16)
Making the denominator equal:
3 × 4 = 12 and 12 > 9
4 × 4 16 16 16
(3:4) > (9:16)
(ii) (5:12) or (17:30)
Making the denominator equal:
5 × 5 = 25 and 17 × 2 = 34
12 × 5 60 30 × 2 60
⇒ 25 < 34
60 60
(5:12) < (17:30)
(iii) (3:7) or (4:9)
Making the denominator equal:
3 × 9 = 27 and 4 × 7 = 28
7 × 9 63 9 â× 7 63
⇒ 27 < 28
63 63
(3:7) < (4:9)
(iv) (1:2) or (13:27)
Making the denominator equal:
1× 27 = 27 and 13 × 2 = 26
2 × 27 54 27 â× 2 54
⇒ 27 > 26
54 54
(1:2) > (13:27)
Answer:
(i) 24 = 24 â÷ 8 = 3 = 3 × 4 = 12
40 40 â÷ 8 5 5 × 4 20
(ii) 36 = 36 â÷ 9 = 4 = 4 × 3 = 12
63 63 â÷ 9 7 7 × 3 21
(iii) 5 = 5 × 4 = 20 = 5 × 7 = 35
7 7 × 4 28 7 × 7 49
Page No 155:
Question 1:
(i) 24 = 24 â÷ 8 = 3 = 3 × 4 = 12
40 40 â÷ 8 5 5 × 4 20
(ii) 36 = 36 â÷ 9 = 4 = 4 × 3 = 12
63 63 â÷ 9 7 7 × 3 21
(iii) 5 = 5 × 4 = 20 = 5 × 7 = 35
7 7 × 4 28 7 × 7 49
Answer:
(i) 4, 6, 8, 12
4 = 4 â÷ 2 = 2 ; 8 = 8 â÷ 4 = 2
6 6 â÷ 2 3 12 12 â÷ 4 3
Hence, 4:9::8:12 are in proportion.
(ii) 7, 42, 13, 78
7 = 7 â÷ 7 = 1 ; 13 = 13 â÷ 13 = 1
42 42 â÷ 7 6 78 78 â÷ 13 6
Hence, 7:42::13:78 are in proportion.
(iii) 33, 121, 9, 96
33 = 33 â÷ 11 = 3 ; 9 = 9 â÷ 3 = 3
121 121 â÷ 11 11 96 96 â÷ 3 32
Hence, 33:121::9:96 are not in proportion.
(iv) 22, 33, 42, 63
Hence, 22:33 :: 42 : 63 are not in proportion.
(v) 32, 48, 70, 210
32 = 32 â÷ 6 = 7 ; 70 = 70 â÷ 70 = 1
48 48 â÷ 6 8 210 210 â÷ 70 3
Hence, 32:48::70:210 are not in proportion.
(vi) 150, 200, 250, 300
150 = 150 â÷ 50 = 3; 250 = 250 â÷ 50 = 5
200 200 â÷ 50 4 300 300 â÷ 50 6
Hence, 150:200::250:300 are not in proportion.
Page No 155:
Question 2:
(i) 4, 6, 8, 12
4 = 4 â÷ 2 = 2 ; 8 = 8 â÷ 4 = 2
6 6 â÷ 2 3 12 12 â÷ 4 3
Hence, 4:9::8:12 are in proportion.
(ii) 7, 42, 13, 78
7 = 7 â÷ 7 = 1 ; 13 = 13 â÷ 13 = 1
42 42 â÷ 7 6 78 78 â÷ 13 6
Hence, 7:42::13:78 are in proportion.
(iii) 33, 121, 9, 96
33 = 33 â÷ 11 = 3 ; 9 = 9 â÷ 3 = 3
121 121 â÷ 11 11 96 96 â÷ 3 32
Hence, 33:121::9:96 are not in proportion.
(iv) 22, 33, 42, 63
Hence, 22:33 :: 42 : 63 are not in proportion.
(v) 32, 48, 70, 210
32 = 32 â÷ 6 = 7 ; 70 = 70 â÷ 70 = 1
48 48 â÷ 6 8 210 210 â÷ 70 3
Hence, 32:48::70:210 are not in proportion.
(vi) 150, 200, 250, 300
150 = 150 â÷ 50 = 3; 250 = 250 â÷ 50 = 5
200 200 â÷ 50 4 300 300 â÷ 50 6
Hence, 150:200::250:300 are not in proportion.
Answer:
(i) 60:105::84:147
60 = 60 â÷ 15 = 4 (H.C.F. of 60 and 105 is 15.)
105 105 â÷ 15 7
84 = 84 â÷ 21 = 4 (H.C.F. of 84 and 147 is 21.)
147 147 â÷ 21 7
Hence, 60:105::84:147 are in proportion.
(ii) 91:104::119:136
91 = 91 â÷ 13 = 7 (H.C.F. of 91 and 104 is 13.)
104 104 â÷ 13 8
119 = 119 â÷ 17 = 7 (H.C.F. of 11 and 136 is 17.)
136 136 â÷ 17 8
Hence, 91:104::119:136 are in proportion.
(iii) 108:72::129:86
108 = 108 â÷ 36 = 3 (H.C.F. of 108 and 72 is 36.)
72 72 â â÷ 36 2
129 = â129 â÷ 43 = 3 (H.C.F. of 129 and 86 is 43.)
86 86 â÷ 43 2
Hence, 108:72::129:86 are in proportion.
(iv) 39:65::141:235
39 = 39 â÷ 13 = 3 (H.C.F. of 39 and 65 is 13.)
65 65 â÷ 13 5
141 = 141 â÷ 47 = 3 (H.C.F. of 141 and 235 is 47.)
235 235 â÷ 47 5
Hence, 39:65::141:235 are in proportion.
Page No 155:
Question 3:
(i) 60:105::84:147
60 = 60 â÷ 15 = 4 (H.C.F. of 60 and 105 is 15.)
105 105 â÷ 15 7
84 = 84 â÷ 21 = 4 (H.C.F. of 84 and 147 is 21.)
147 147 â÷ 21 7
Hence, 60:105::84:147 are in proportion.
(ii) 91:104::119:136
91 = 91 â÷ 13 = 7 (H.C.F. of 91 and 104 is 13.)
104 104 â÷ 13 8
119 = 119 â÷ 17 = 7 (H.C.F. of 11 and 136 is 17.)
136 136 â÷ 17 8
Hence, 91:104::119:136 are in proportion.
(iii) 108:72::129:86
108 = 108 â÷ 36 = 3 (H.C.F. of 108 and 72 is 36.)
72 72 â â÷ 36 2
129 = â129 â÷ 43 = 3 (H.C.F. of 129 and 86 is 43.)
86 86 â÷ 43 2
Hence, 108:72::129:86 are in proportion.
(iv) 39:65::141:235
39 = 39 â÷ 13 = 3 (H.C.F. of 39 and 65 is 13.)
65 65 â÷ 13 5
141 = 141 â÷ 47 = 3 (H.C.F. of 141 and 235 is 47.)
235 235 â÷ 47 5
Hence, 39:65::141:235 are in proportion.
Answer:
(i) 55:11::x:6
Product of extremes = Product of means
55 × 6 = 11 × x
⇒ 11x = 330
⇒ x = 330 = 30
11
(ii) 27:x::63:84
Product of extremes = Product of means
27 â× 84 = x â× 63
⇒ 63x = 2268
⇒ x = 2268 = 36
63
(iii) 51:85::57:x
Product of extremes = Product of means
51 × x = 85 × 57
⇒ 51x = 4845
⇒ x = 4845 = 95
51
(iv) x:92::87:116
Product of extremes = Product of means
x × 116 = 92 â× 87
⇒ 116x = 8004
⇒ x = 8004 = 69
116
Page No 155:
Question 4:
(i) 55:11::x:6
Product of extremes = Product of means
55 × 6 = 11 × x
⇒ 11x = 330
⇒ x = 330 = 30
11
(ii) 27:x::63:84
Product of extremes = Product of means
27 â× 84 = x â× 63
⇒ 63x = 2268
⇒ x = 2268 = 36
63
(iii) 51:85::57:x
Product of extremes = Product of means
51 × x = 85 × 57
⇒ 51x = 4845
⇒ x = 4845 = 95
51
(iv) x:92::87:116
Product of extremes = Product of means
x × 116 = 92 â× 87
⇒ 116x = 8004
⇒ x = 8004 = 69
116
Answer:
(i) 51:68::85:102
Product of means = 68 × 85 = 5780
Product of extremes = 51 × 102 = 5202
Product of means ≠ Product of extremes
Hence, (F).
(ii) 36:45::80:100
Product of means = 45 â× 80 = 3600
Product of extremes = 36 × 100 = 3600
Product of means = Product of extremes
Hence, (T).
(iii) 30 bags:18 bags::Rs 450:Rs 270
or 30:18::450:270
Product of means = 18 × 450 = 8100
Product of extremes = 30 â× 270 = 8100
Product of means = Product of extremes
Hence, (T).
(iv) 81 kg:45 kg::18 men:10 men
or 81:45::18:10
Product of means = 45 × 18 = 810
Product of extremes = 81 × 10 = 810
Product of means = Product of extremes
Hence, (T).
(v) 45 km:60 km::12 h:15 h
or,45:60::12:15
Product of means = 60 × 12 = 720
Product of extremes = 45 × 15 = 675
Product of means ≠ Product of extremes
Hence, (F).
(vi) 32 kg:Rs 36::8 kg:Rs 9
Product of means = 36 × 8 = 288
Product of extremes = 32 × 9 = 288
Product of means = Product of extremes
Hence, (T).
Page No 155:
Question 5:
(i) 51:68::85:102
Product of means = 68 × 85 = 5780
Product of extremes = 51 × 102 = 5202
Product of means ≠ Product of extremes
Hence, (F).
(ii) 36:45::80:100
Product of means = 45 â× 80 = 3600
Product of extremes = 36 × 100 = 3600
Product of means = Product of extremes
Hence, (T).
(iii) 30 bags:18 bags::Rs 450:Rs 270
or 30:18::450:270
Product of means = 18 × 450 = 8100
Product of extremes = 30 â× 270 = 8100
Product of means = Product of extremes
Hence, (T).
(iv) 81 kg:45 kg::18 men:10 men
or 81:45::18:10
Product of means = 45 × 18 = 810
Product of extremes = 81 × 10 = 810
Product of means = Product of extremes
Hence, (T).
(v) 45 km:60 km::12 h:15 h
or,45:60::12:15
Product of means = 60 × 12 = 720
Product of extremes = 45 × 15 = 675
Product of means ≠ Product of extremes
Hence, (F).
(vi) 32 kg:Rs 36::8 kg:Rs 9
Product of means = 36 × 8 = 288
Product of extremes = 32 × 9 = 288
Product of means = Product of extremes
Hence, (T).
Answer:
(i) 25 cm:1 m and Rs 40:Rs 160 (or) 25 cm:100 cm and Rs 40:Rs 160
25 = 25 â÷ 25 = 1 and 40 = 40 ÷ 40 = 1
100 100 ââ÷ 25 4 160 160 â÷ 40 4
Hence, they are in proportion.
(ii) 39 litres:65 litres and 6 bottles:10 bottles
39 = 39 â÷ 13 = 3 and 6 = 6 â÷ 2 = 3
65 65 ââ÷ 13 5 10 10 â÷ 2 5
Hence they are in proportion.
(iii) 200 mL:2.5 L and Rs 4:Rs 50 (or) 200 mL:2500 mL and Rs 4:Rs 50
200 = 2 and 4 = 4 â÷ 2 = 2
2500 25 50 50 ÷ 2 25
Hence, they are in proportion.
(iv) 2 kg:80 kg and 25 g:625 kg (or) 2 kg:80 kg and 25 g:625000 g
2 = 2 â÷ 2 = 1 and 25 = 25 â÷ 25 = 1
80 80 â÷ 2 40 625000 625000 ââ÷ 25 25000
Hence, they are not in proportion.
Page No 155:
Question 6:
(i) 25 cm:1 m and Rs 40:Rs 160 (or) 25 cm:100 cm and Rs 40:Rs 160
25 = 25 â÷ 25 = 1 and 40 = 40 ÷ 40 = 1
100 100 ââ÷ 25 4 160 160 â÷ 40 4
Hence, they are in proportion.
(ii) 39 litres:65 litres and 6 bottles:10 bottles
39 = 39 â÷ 13 = 3 and 6 = 6 â÷ 2 = 3
65 65 ââ÷ 13 5 10 10 â÷ 2 5
Hence they are in proportion.
(iii) 200 mL:2.5 L and Rs 4:Rs 50 (or) 200 mL:2500 mL and Rs 4:Rs 50
200 = 2 and 4 = 4 â÷ 2 = 2
2500 25 50 50 ÷ 2 25
Hence, they are in proportion.
(iv) 2 kg:80 kg and 25 g:625 kg (or) 2 kg:80 kg and 25 g:625000 g
2 = 2 â÷ 2 = 1 and 25 = 25 â÷ 25 = 1
80 80 â÷ 2 40 625000 625000 ââ÷ 25 25000
Hence, they are not in proportion.
Answer:
Let the 3rd term be x.
Thus, 51:68::x:108
We know:
Product of extremes = Product of means
51 × 108 = 68 × x
⇒ 5508 = 68x
⇒ x = 5508 = 81
68
Hence, the third term is 81.
Page No 155:
Question 7:
Let the 3rd term be x.
Thus, 51:68::x:108
We know:
Product of extremes = Product of means
51 × 108 = 68 × x
⇒ 5508 = 68x
⇒ x = 5508 = 81
68
Hence, the third term is 81.
Answer:
Let the second term be x.
Then. 12:x::8:14
We know:
Product of extremes = Product of means
12 × 14 = 8x
⇒ 168 = 8x
â ⇒ x = 168 = 21
8
Hence, the second term is 21.
Page No 155:
Question 8:
Let the second term be x.
Then. 12:x::8:14
We know:
Product of extremes = Product of means
12 × 14 = 8x
⇒ 168 = 8x
â ⇒ x = 168 = 21
8
Hence, the second term is 21.
Answer:
(i) 48:60, 60:75
Product of means = 60 × 60 = 3600
Product of extremes = 48 × 75 = 3600
Product of means = Product of extremes
Hence, 48:60::60:75 are in continued proportion.
(ii) 36:90, 90:225
Product of means = 90 × 90 = 8100
Product of extremes = 36 × 225 = 8100
Product of means = Product of extremes
Hence, 36:90::90:225 are in continued proportion.
(iii) 16:84, 84:441
Product of means = 84 × 84 = 7056
Product of extremes = 16 × 441 = 7056
Product of means = Product of extremes
Hence, 16:84::84:441 are in continued proportion.
Page No 155:
Question 9:
(i) 48:60, 60:75
Product of means = 60 × 60 = 3600
Product of extremes = 48 × 75 = 3600
Product of means = Product of extremes
Hence, 48:60::60:75 are in continued proportion.
(ii) 36:90, 90:225
Product of means = 90 × 90 = 8100
Product of extremes = 36 × 225 = 8100
Product of means = Product of extremes
Hence, 36:90::90:225 are in continued proportion.
(iii) 16:84, 84:441
Product of means = 84 × 84 = 7056
Product of extremes = 16 × 441 = 7056
Product of means = Product of extremes
Hence, 16:84::84:441 are in continued proportion.
Answer:
Given: 9:x::x:49
We know:
Product of means = Product of extremes
x × x = 9 × 49
⇒ x2 = 441
⇒ x2 = (21)2
⇒ x = 21
Page No 155:
Question 10:
Given: 9:x::x:49
We know:
Product of means = Product of extremes
x × x = 9 × 49
⇒ x2 = 441
⇒ x2 = (21)2
⇒ x = 21
Answer:
Let the height of the pole = x m
Then, we have:
x:20::6:8
Now, we know:
Product of extremes = Product of means
8x = 20â × 6
x = 120 = 15
8
âHence, the height of the pole is 15 m.
Page No 155:
Question 11:
Let the height of the pole = x m
Then, we have:
x:20::6:8
Now, we know:
Product of extremes = Product of means
8x = 20â × 6
x = 120 = 15
8
âHence, the height of the pole is 15 m.
Answer:
5:3::x:6
We know:
Product of means = Product of extremes
3x = 5 â× 6
⇒ x = 30 = 10
3
x = 10
Page No 157:
Question 1:
5:3::x:6
We know:
Product of means = Product of extremes
3x = 5 â× 6
⇒ x = 30 = 10
3
x = 10
Answer:
Cost of 14 m of cloth = Rs 1890
Cost of 1 m of cloth = 1890 = Rs 135
14
Cost of 6 m of cloth = 6â × 135 = Rs 810
Page No 157:
Question 2:
Cost of 14 m of cloth = Rs 1890
Cost of 1 m of cloth = 1890 = Rs 135
14
Cost of 6 m of cloth = 6â × 135 = Rs 810
Answer:
Cost of dozen soaps = Rs 285.60
Cost of 1 soap = 285.60
12
Cost of 15 soaps = 15â × 285.60 = 4284 = Rs 357
12 12
Page No 157:
Question 3:
Cost of dozen soaps = Rs 285.60
Cost of 1 soap = 285.60
12
Cost of 15 soaps = 15â × 285.60 = 4284 = Rs 357
12 12
Answer:
Cost of 9 kg of rice = Rs 327.60
Cost of 1 kg of rice = 327.60
9
Cost of 50 kg of rice = 50â × 327.60 = 16380 = Rs 1820
9 9
Hence, the cost of 50 kg of rice is Rs 1820.
Page No 157:
Question 4:
Cost of 9 kg of rice = Rs 327.60
Cost of 1 kg of rice = 327.60
9
Cost of 50 kg of rice = 50â × 327.60 = 16380 = Rs 1820
9 9
Hence, the cost of 50 kg of rice is Rs 1820.
Answer:
Weight of 22.5 m of uniform iron rod = 85.5 kg
Weight of 1 m of uniform iron rod = 85.5 kg
22.5
Weight of 5 m of uniform iron rod = 5â × 85.5 = 427.5 = 19 kg
22.5 22.5
Thus, the weight of 5 m of iron rod is 19 kg.
Page No 157:
Question 5:
Weight of 22.5 m of uniform iron rod = 85.5 kg
Weight of 1 m of uniform iron rod = 85.5 kg
22.5
Weight of 5 m of uniform iron rod = 5â × 85.5 = 427.5 = 19 kg
22.5 22.5
Thus, the weight of 5 m of iron rod is 19 kg.
Answer:
Oil contained by 15 tins = 234 kg
Oil contained by 1 tin = 234 kg
15
Oil contained by 10 tins = 10 × 234 = 2340 = 156 kg
15 15
Page No 157:
Question 6:
Oil contained by 15 tins = 234 kg
Oil contained by 1 tin = 234 kg
15
Oil contained by 10 tins = 10 × 234 = 2340 = 156 kg
15 15
Answer:
Distance covered by a car in 12 L diesel = 222 km
Distance covered by it in 1 L diesel = 222 km
12
Distance covered by it in 22 L diesel = 22 × 222 = 4884 = 407 km
12 12
Page No 157:
Question 7:
Distance covered by a car in 12 L diesel = 222 km
Distance covered by it in 1 L diesel = 222 km
12
Distance covered by it in 22 L diesel = 22 × 222 = 4884 = 407 km
12 12
Answer:
Cost of transporting 25 tonnes of weight = Rs 540
Cost of transporting 1 tone of weight = 540
25
Cost of transporting 35 tonnes of weight = 35â × 540 = 18900 = Rs 756
25 25
Page No 158:
Question 8:
Cost of transporting 25 tonnes of weight = Rs 540
Cost of transporting 1 tone of weight = 540
25
Cost of transporting 35 tonnes of weight = 35â × 540 = 18900 = Rs 756
25 25
Answer:
Let the weight of copper be x g.
âThen, 4.5:3.5::18.9:x
Product of extremes = Product of means
4.5 × x = 3.5 × 18.9
⇒ x = 66.15 = 14.7
4.5
So, the weight of copper is 14.7 g.
Page No 158:
Question 9:
Let the weight of copper be x g.
âThen, 4.5:3.5::18.9:x
Product of extremes = Product of means
4.5 × x = 3.5 × 18.9
⇒ x = 66.15 = 14.7
4.5
So, the weight of copper is 14.7 g.
Answer:
Number of inland letters whose total cost is Rs 87.50 = 35
Number of inland letters of whose cost is Re 1 = 35
87.50
Number of inland letters whose cost is Rs 315 = 315â × 35 = 11025 = 126
87.50 87.50
Hence, we can buy 126 inland letters for Rs 315.
Page No 158:
Question 10:
Number of inland letters whose total cost is Rs 87.50 = 35
Number of inland letters of whose cost is Re 1 = 35
87.50
Number of inland letters whose cost is Rs 315 = 315â × 35 = 11025 = 126
87.50 87.50
Hence, we can buy 126 inland letters for Rs 315.
Answer:
Number of bananas that can be purchased for Rs 104 = 48 (4 dozen)
Number of bananas that can be purchased for Re 1 = 48
104
Number of bananas that can be purchased for Rs 6.50 = 6.50 × 48 = 312 = 3
104 104
Hence, 3 bananas can be purchased for Rs 6.50.
Page No 158:
Question 11:
Number of bananas that can be purchased for Rs 104 = 48 (4 dozen)
Number of bananas that can be purchased for Re 1 = 48
104
Number of bananas that can be purchased for Rs 6.50 = 6.50 × 48 = 312 = 3
104 104
Hence, 3 bananas can be purchased for Rs 6.50.
Answer:
Number of chairs that can be bought for Rs 22770 = 18
Number of chairs that can be bought for Re 1 = 18
22770
Number of chairs that can be bought for Rs 10120 = 10120 × 18 = 182160 = 8
22770 22770
Page No 158:
Question 12:
Number of chairs that can be bought for Rs 22770 = 18
Number of chairs that can be bought for Re 1 = 18
22770
Number of chairs that can be bought for Rs 10120 = 10120 × 18 = 182160 = 8
22770 22770
Answer:
(i) Time taken by the car to travel 195 km = 3 hours
Time taken by it to travel 1 km = 3 hours
195
Time taken by it to travel 520 km = 520 × 3 = 1560 = 8 hours
195 195
(ii) Distance covered by the car in 3 hours = 195 km
Distance covered by it in 1 hour = 195 = 65 km
3
Distance covered by it in 7 hours = 7 × 65 = 455 km
Page No 158:
Question 13:
(i) Time taken by the car to travel 195 km = 3 hours
Time taken by it to travel 1 km = 3 hours
195
Time taken by it to travel 520 km = 520 × 3 = 1560 = 8 hours
195 195
(ii) Distance covered by the car in 3 hours = 195 km
Distance covered by it in 1 hour = 195 = 65 km
3
Distance covered by it in 7 hours = 7 × 65 = 455 km
Answer:
(i) Earning of a labourer in 12 days = Rs 1980
Earning of the labourer in 1 day = 1980 = Rs 165
12
Earning of the labourer in 7 days = 7â × 165 = Rs 1155
(ii) Number of days taken by the labourer to earn Rs 1980 = 12 days
Number of days taken by him to earn Re 1 = 12 days
1980
Number of days taken by him to earn Rs 2640 = 2640 × 12 = 31680 = 16 days
1980 1980
Page No 158:
Question 14:
(i) Earning of a labourer in 12 days = Rs 1980
Earning of the labourer in 1 day = 1980 = Rs 165
12
Earning of the labourer in 7 days = 7â × 165 = Rs 1155
(ii) Number of days taken by the labourer to earn Rs 1980 = 12 days
Number of days taken by him to earn Re 1 = 12 days
1980
Number of days taken by him to earn Rs 2640 = 2640 × 12 = 31680 = 16 days
1980 1980
Answer:
Weight of 65 books = 13 kg
(i) Weight of 1 book = 13 kg
65
Weight of 80 books = 80 × 13 = 1040 = 16 kg
65 65
(ii) Number of books weighing 13 kg = 65
Number of books weighing 1 kg = 65 = 5
13
Number of books weighing 6.4 kg = 6.4 × 5 = 32
Page No 158:
Question 15:
Weight of 65 books = 13 kg
(i) Weight of 1 book = 13 kg
65
Weight of 80 books = 80 × 13 = 1040 = 16 kg
65 65
(ii) Number of books weighing 13 kg = 65
Number of books weighing 1 kg = 65 = 5
13
Number of books weighing 6.4 kg = 6.4 × 5 = 32
Answer:
Number of boxes containing 6000 pens = 48
Number of boxes containing 1 pen = 48
6000
Number of boxes containing 1875 pens = 1875 × 48 = 90000 = 15
6000 6000
15 boxes are needed for 1875 pens.
Page No 158:
Question 16:
Number of boxes containing 6000 pens = 48
Number of boxes containing 1 pen = 48
6000
Number of boxes containing 1875 pens = 1875 × 48 = 90000 = 15
6000 6000
15 boxes are needed for 1875 pens.
Answer:
Number of days taken by 24 workers to build a wall = 15 days
Number of days taken by 1 worker to build the wall = 15 × 24 = 360 days (less worker means more days)
Number of days taken by 9 workers to build the wall = 360 = 40 days
9
Page No 158:
Question 17:
Number of days taken by 24 workers to build a wall = 15 days
Number of days taken by 1 worker to build the wall = 15 × 24 = 360 days (less worker means more days)
Number of days taken by 9 workers to build the wall = 360 = 40 days
9
Answer:
Number of men required to complete the work in 26 days = 40
Number of men required to complete the work in 1 day = 40 × 26 = 1040 men (less men more days)
Number of men required to complete the work in 16 days = 1040 = 65
16
Page No 158:
Question 18:
Number of men required to complete the work in 26 days = 40
Number of men required to complete the work in 1 day = 40 × 26 = 1040 men (less men more days)
Number of men required to complete the work in 16 days = 1040 = 65
16
Answer:
Number of days the provisions will last for 550 men = 28 days
Number of days the provisions will last for 1 man = 28 × 550 = 15400 days (less men means more days)
Number of days the provisions will last for 700 men = 15400 = 22 days
700
The provision will last for 22 days.
Page No 158:
Question 19:
Number of days the provisions will last for 550 men = 28 days
Number of days the provisions will last for 1 man = 28 × 550 = 15400 days (less men means more days)
Number of days the provisions will last for 700 men = 15400 = 22 days
700
The provision will last for 22 days.
Answer:
Number of days for which the given quantity of rice is sufficient for 60 persons = 3 days
Number of days for which it is sufficient for 1 person = 3 × 60 = 180 days (less men means more days )
Number of days for which it is sufficient for 18 persons = 180 = 10 days
18
Page No 158:
Question 1:
Number of days for which the given quantity of rice is sufficient for 60 persons = 3 days
Number of days for which it is sufficient for 1 person = 3 × 60 = 180 days (less men means more days )
Number of days for which it is sufficient for 18 persons = 180 = 10 days
18
Answer:
(d) 4 : 5
92:115 = 92 â÷ 23 = 4 (As H.C.F. of 92 and 115 is 23.)
115 â÷ 23 5
Page No 158:
Question 2:
(d) 4 : 5
92:115 = 92 â÷ 23 = 4 (As H.C.F. of 92 and 115 is 23.)
115 â÷ 23 5
Answer:
(a) 95
57:x::51:85
57 = 51
x 85
⇒ x = 57 × 85
51
⇒ x = 4845 = 95
51
Page No 158:
Question 3:
(a) 95
57:x::51:85
57 = 51
x 85
⇒ x = 57 × 85
51
⇒ x = 4845 = 95
51
Answer:
(a) 63
25:35::45:x
25 = 45
35 x
⇒ x = 35 × 45 = 1575 = 63
25 25
Page No 158:
Question 4:
(a) 63
25:35::45:x
25 = 45
35 x
⇒ x = 35 × 45 = 1575 = 63
25 25
Answer:
(c) 28
4:5::x:35
⇒ 4 = x
5 35
⇒ x = 4 × 35 = 4 × 7 = 28
5
Page No 158:
Question 5:
(c) 28
4:5::x:35
⇒ 4 = x
5 35
⇒ x = 4 × 35 = 4 × 7 = 28
5
Answer:
(b) ad = bc
Given:
a, b, c, d are in proportion.
a:b::c:d
a = c
b d
⇒ ad = bc
Page No 158:
Question 6:
(b) ad = bc
Given:
a, b, c, d are in proportion.
a:b::c:d
a = c
b d
⇒ ad = bc
Answer:
(b) b2 = ac
Given:
a, b, c are in proportion.
a:b::b:c
Product of means = Product of extremes
⇒â bâ2 = ac
Page No 158:
Question 7:
(b) b2 = ac
Given:
a, b, c are in proportion.
a:b::b:c
Product of means = Product of extremes
⇒â bâ2 = ac
Answer:
(b) (5 : 8) < (3 : 4)
We can write
Making the denominator equal:
5 and 3 × 2 = 6
8 4 × 2 8
As 6 > 5, 5 < 3
8 4
Page No 159:
Question 8:
(b) (5 : 8) < (3 : 4)
We can write
Making the denominator equal:
5 and 3 × 2 = 6
8 4 × 2 8
As 6 > 5, 5 < 3
8 4
Answer:
(a) Rs 440
A:B = 8:11
Sum of ratio terms = 8 + 11 = 19
B's share = 11 × 760 = 8360 = Rs 440
19 19
Page No 159:
Question 9:
(a) Rs 440
A:B = 8:11
Sum of ratio terms = 8 + 11 = 19
B's share = 11 × 760 = 8360 = Rs 440
19 19
Answer:
(d) 147
Ratio = 5:7
Let x be any number such that we have:
5x + 7x = 252
⇒ 12x = 252
⇒ x = 252 = 21
12
Now, 5x = 5 × 21= 105
7x = 7 × 21 = 147
The largest number is 147.
Page No 159:
Question 10:
(d) 147
Ratio = 5:7
Let x be any number such that we have:
5x + 7x = 252
⇒ 12x = 252
⇒ x = 252 = 21
12
Now, 5x = 5 × 21= 105
7x = 7 × 21 = 147
The largest number is 147.
Answer:
(b) 50 cm
The sides of the triangle are in the ratio 1:3:5.
Let x be any number such that the sides are 1x cm, 3x cm and 5x cm.
1x + 3x + 5x = 90
⇒ 9x = 90
â⇒ x = 90 = 10
9
First side = 1x = 1 â× 10 = 10 cm
Second side = 3x = 3 â× 10 = 30 cm
Third side = 5x = 5 × 10 = 50 cm
The length of the largest side is 50 cm.
Page No 159:
Question 11:
(b) 50 cm
The sides of the triangle are in the ratio 1:3:5.
Let x be any number such that the sides are 1x cm, 3x cm and 5x cm.
1x + 3x + 5x = 90
⇒ 9x = 90
â⇒ x = 90 = 10
9
First side = 1x = 1 â× 10 = 10 cm
Second side = 3x = 3 â× 10 = 30 cm
Third side = 5x = 5 × 10 = 50 cm
The length of the largest side is 50 cm.
Answer:
(c) 2856
Ratio of boys and girls = 12:5
Let x be any number such that the number of boys and girls are 12x and 5x, respectively.
Number of girls = 840
5x = 840
⇒ x = 840 = 168
5
Number of boys = 12x = 12 × 168 = 2016
Number of girls = 840
Total strength of the school = 2016 + 840 = 2856
Page No 159:
Question 12:
(c) 2856
Ratio of boys and girls = 12:5
Let x be any number such that the number of boys and girls are 12x and 5x, respectively.
Number of girls = 840
5x = 840
⇒ x = 840 = 168
5
Number of boys = 12x = 12 × 168 = 2016
Number of girls = 840
Total strength of the school = 2016 + 840 = 2856
Answer:
(b) Rs 161
Cost of 12 pens = Rs 138
Cost of 1 pen = Rs 138
12
Cost of 14 pens = Rs 138 × 14 = Rs 1932 = Rs 161
12 12
Page No 159:
Question 13:
(b) Rs 161
Cost of 12 pens = Rs 138
Cost of 1 pen = Rs 138
12
Cost of 14 pens = Rs 138 × 14 = Rs 1932 = Rs 161
12 12
Answer:
(b) 45 days
Time taken by 24 workers to build a wall = 15 days
Time taken by 1 worker to build a wall = 24 × 15 = 360 days (clearly less workers will take more time to build a wall)
Time taken by 8 workers to build a wall = 360 = 45 days
8
Page No 159:
Question 14:
(b) 45 days
Time taken by 24 workers to build a wall = 15 days
Time taken by 1 worker to build a wall = 24 × 15 = 360 days (clearly less workers will take more time to build a wall)
Time taken by 8 workers to build a wall = 360 = 45 days
8
Answer:
(a) 52
Number of men required to finish the work in 26 days = 40
Number of men required to finish it in 1 day = 40 × 26 = 1040 men (More men means less days)
Number of men required to finish it in 20 days = 1040 = 52
20
Page No 159:
Question 15:
(a) 52
Number of men required to finish the work in 26 days = 40
Number of men required to finish it in 1 day = 40 × 26 = 1040 men (More men means less days)
Number of men required to finish it in 20 days = 1040 = 52
20
Answer:
(b) 185 km
Distance covered in 6 L of petrol = 111 km
Distance covered in 1 L of petrol = 111 km
6
Distance covered in 10 L of petrol = 111 × 10 = 1110 = 185 km
6 6
Page No 159:
Question 16:
(b) 185 km
Distance covered in 6 L of petrol = 111 km
Distance covered in 1 L of petrol = 111 km
6
Distance covered in 10 L of petrol = 111 × 10 = 1110 = 185 km
6 6
Answer:
(a) 22 days
Number of days for which 550 men had provisions = 28 days
Number of days for which 1 man had provisions = 28 × 550 = 15400 days (more men means less days)
Number of days for which 700 men had provisions = 15400 = 22 days
700
Page No 159:
Question 17:
(a) 22 days
Number of days for which 550 men had provisions = 28 days
Number of days for which 1 man had provisions = 28 × 550 = 15400 days (more men means less days)
Number of days for which 700 men had provisions = 15400 = 22 days
700
Answer:
(c) 90°
Ratio of the angles of a triangle is 3:1: 2
Let x be any number such that the three angles are (3x), (1x) and (2x).
We know, the sum of the angles of a triangle is 180.
3x + 1x + 2x = 180
⇒ 6x = 180
â ⇒ x = 180 = 30
6
(3x ) = (3 â× 30) = 90o
â (1x) = (1â × 30) = 30o
â (2x) = (2 × 30) = 60o
The measure of the largest angle is 90oâ.
Page No 159:
Question 18:
(c) 90°
Ratio of the angles of a triangle is 3:1: 2
Let x be any number such that the three angles are (3x), (1x) and (2x).
We know, the sum of the angles of a triangle is 180.
3x + 1x + 2x = 180
⇒ 6x = 180
â ⇒ x = 180 = 30
6
(3x ) = (3 â× 30) = 90o
â (1x) = (1â × 30) = 30o
â (2x) = (2 × 30) = 60o
The measure of the largest angle is 90oâ.
Answer:
(b) 45 m
Length:Breadth = 5:4
Let x be any number such that the length and the breadth are 5x and 4x, respectively.
Now , 4x = 36
x = 36 = 9
4
Length = 5x = 5 × 9 = 45 m
Page No 159:
Question 19:
(b) 45 m
Length:Breadth = 5:4
Let x be any number such that the length and the breadth are 5x and 4x, respectively.
Now , 4x = 36
x = 36 = 9
4
Length = 5x = 5 × 9 = 45 m
Answer:
(a) 13 : 15
Speed = Distance
Time
Speed of the bus = 195 km = 65 km/hr
3 hr
Speed of the train = 300 km = 75 km/hr
4 hr
Ratio = 65 = 65 ÷ 5 = 13 = 13:15
75 75 ÷ 5 15
Page No 159:
Question 20:
(a) 13 : 15
Speed = Distance
Time
Speed of the bus = 195 km = 65 km/hr
3 hr
Speed of the train = 300 km = 75 km/hr
4 hr
Ratio = 65 = 65 ÷ 5 = 13 = 13:15
75 75 ÷ 5 15
Answer:
(c) Rs 198
Cost of 5 bars of soap = Rs 82.50
Cost of 1 bar of soap = 82.50 = Rs 16.5
5
Cost of 12 (1 dozen) bars of soap = 16.5 × 12 = Rs 198
Page No 159:
Question 21:
(c) Rs 198
Cost of 5 bars of soap = Rs 82.50
Cost of 1 bar of soap = 82.50 = Rs 16.5
5
Cost of 12 (1 dozen) bars of soap = 16.5 × 12 = Rs 198
Answer:
(b) Rs 750
Cost of 30 packets of 8 pencils each = Rs 600
Cost of 1 packet of 8 pencils = 600 = Rs 20
30
Cost of 1 pencil = Rs 20
8
Cost of 1 packet of 12 pencils = 12â × 20 = 240 = Rs 30
8 8
Cost of 25 packets of 12 pencils each = 25 × 30 = Rs 750
Page No 159:
Question 22:
(b) Rs 750
Cost of 30 packets of 8 pencils each = Rs 600
Cost of 1 packet of 8 pencils = 600 = Rs 20
30
Cost of 1 pencil = Rs 20
8
Cost of 1 packet of 12 pencils = 12â × 20 = 240 = Rs 30
8 8
Cost of 25 packets of 12 pencils each = 25 × 30 = Rs 750
Answer:
(a) Rs 344
Cost of rail journey of 75 km = Rs 215
Cost of rail journey of 1 km = Rs 215
75
Cost of rail journey of 120 km = 120â × 215 = 25800 = Rs 344
75 75
Page No 159:
Question 23:
(a) Rs 344
Cost of rail journey of 75 km = Rs 215
Cost of rail journey of 1 km = Rs 215
75
Cost of rail journey of 120 km = 120â × 215 = 25800 = Rs 344
75 75
Answer:
(d) 8
Let the third term be x.
Then, we have:
12:21::x:14
We know:
Product of means = Product of extremes
21x = 12 × 14
⇒ 21x = 168
⇒ x = 168 = 8
21
The third term is 8
Page No 159:
Question 24:
(d) 8
Let the third term be x.
Then, we have:
12:21::x:14
We know:
Product of means = Product of extremes
21x = 12 × 14
⇒ 21x = 168
⇒ x = 168 = 8
21
The third term is 8
Answer:
(b) 15 h
Time taken by 10 boys to dig a pitch = 12 hours
Time taken by 1 boy to dig a pitch = 12 × 10 = 120 hours (less boys means more time)
Time taken by 8 boys to dig a pitch = 120 = 15 hours
8
Page No 161:
Question 1:
(b) 15 h
Time taken by 10 boys to dig a pitch = 12 hours
Time taken by 1 boy to dig a pitch = 12 × 10 = 120 hours (less boys means more time)
Time taken by 8 boys to dig a pitch = 120 = 15 hours
8
Answer:
(a) 90 cm:1.05 m (or) 90 cm:105 cm (1 m = 100 cm)
90 = 90 â÷ 15 = 6 (H.C.F. of 90 and 105 is 15.)
105 105 â÷ 15 7
6:7
(b) 35 minutes to an hour (or) 35 minutes:60 minutes (1 hour = 60 minutes)
35 = 35 â÷ 5 = 7 (H.C.F. of 35 and 60 is 5.)
60 60 â÷ 5 12
7:12
(c) 150 mL to 2 L (or) 150 L:2000 L (1 L= 1000 mL)
150 = 150 â÷ 50 = 3 (HCF of 150 and 2000 is 50)
2000 2000â â÷50 40
3:40
(d) 2 dozens to a score (or) 24:20 (1 dozen = 12 and 1 score = 20)
24 = 24 â÷ 4 = 6 (H.C.F. of 24 and 20 is 4)
20 20â â÷ 4 5
6:5
Page No 161:
Question 2:
(a) 90 cm:1.05 m (or) 90 cm:105 cm (1 m = 100 cm)
90 = 90 â÷ 15 = 6 (H.C.F. of 90 and 105 is 15.)
105 105 â÷ 15 7
6:7
(b) 35 minutes to an hour (or) 35 minutes:60 minutes (1 hour = 60 minutes)
35 = 35 â÷ 5 = 7 (H.C.F. of 35 and 60 is 5.)
60 60 â÷ 5 12
7:12
(c) 150 mL to 2 L (or) 150 L:2000 L (1 L= 1000 mL)
150 = 150 â÷ 50 = 3 (HCF of 150 and 2000 is 50)
2000 2000â â÷50 40
3:40
(d) 2 dozens to a score (or) 24:20 (1 dozen = 12 and 1 score = 20)
24 = 24 â÷ 4 = 6 (H.C.F. of 24 and 20 is 4)
20 20â â÷ 4 5
6:5
Answer:
Ratio of zinc and copper in an alloy is = 7:9
Let the weight of zinc and copper in it be (7x) and (9x), respectively.
Now, the weight of a copper = 12.6 kg (given)
∴ 9x = 12.6
⇒ x = 12.6 = 1.4
9
∴ Weight of zinc = 7x = 7â × 1.4 = 9.8 kg
Page No 161:
Question 3:
Ratio of zinc and copper in an alloy is = 7:9
Let the weight of zinc and copper in it be (7x) and (9x), respectively.
Now, the weight of a copper = 12.6 kg (given)
∴ 9x = 12.6
⇒ x = 12.6 = 1.4
9
∴ Weight of zinc = 7x = 7â × 1.4 = 9.8 kg
Answer:
Given:
A:B:C = 2:3:5
Sum of ratio = 2 + 3 + 5 = 10
Total money = Rs 1400
Then, share of A = 2 × Rs 1400 = Rs 2800 = Rs 280
10 10
Share of B = 3 â× Rs 1400 = Rs 4200 = Rs 420
10 10
Share of C = 5 â× Rs 1400 = Rs 7000 = Rs 700
10 10
Page No 161:
Question 4:
Given:
A:B:C = 2:3:5
Sum of ratio = 2 + 3 + 5 = 10
Total money = Rs 1400
Then, share of A = 2 × Rs 1400 = Rs 2800 = Rs 280
10 10
Share of B = 3 â× Rs 1400 = Rs 4200 = Rs 420
10 10
Share of C = 5 â× Rs 1400 = Rs 7000 = Rs 700
10 10
Answer:
We can write:
By making their denominators same: (Taking the L.C.M. of 6 and 4, which is 24.)
Consider, 5:6
5 â× 4 = 20
6 â× 4 24
And, 3 â× 6 = 18
4 â× 6 24
As 20 > 18
Clearly, (5:6) > (3:4)
Page No 161:
Question 5:
We can write:
By making their denominators same: (Taking the L.C.M. of 6 and 4, which is 24.)
Consider, 5:6
5 â× 4 = 20
6 â× 4 24
And, 3 â× 6 = 18
4 â× 6 24
As 20 > 18
Clearly, (5:6) > (3:4)
Answer:
Number of men needed to finish a piece of work in 26 days = 40
Number of men needed to finish it in 1 day = 26 × 40 = 1040 (less days means more men)
Number of men needed to finish it in 16 days = 1040 = 65
16
Page No 161:
Question 6:
Number of men needed to finish a piece of work in 26 days = 40
Number of men needed to finish it in 1 day = 26 × 40 = 1040 (less days means more men)
Number of men needed to finish it in 16 days = 1040 = 65
16
Answer:
Number of days for which provisions last for 425 men = 30 days
Number of days for which provisions last for 1 men = 30 × 425 = 12750 days. (less men means more days)
Number of days for which provisions last for 375 men = 12750 = 34 days
375
Hence, provisions will last for 34 days for 375 men.
Page No 161:
Question 7:
Number of days for which provisions last for 425 men = 30 days
Number of days for which provisions last for 1 men = 30 × 425 = 12750 days. (less men means more days)
Number of days for which provisions last for 375 men = 12750 = 34 days
375
Hence, provisions will last for 34 days for 375 men.
Answer:
Given:
36:x::x:16
We know:
Product of means = Product of extremes
x × x = 36 × 16
⇒ x2 = 576
⇒ x2 = 242
⇒ x = 24
Page No 161:
Question 8:
Given:
36:x::x:16
We know:
Product of means = Product of extremes
x × x = 36 × 16
⇒ x2 = 576
⇒ x2 = 242
⇒ x = 24
Answer:
Consider 48:60::60:75
Product of means = 60 × 60 = 3600
Product of extremes = 48 × 75 = 3600
So product of means = Product of extremes
Hence, 48, 60, 75 are in continued proportion.
Page No 161:
Question 9:
Consider 48:60::60:75
Product of means = 60 × 60 = 3600
Product of extremes = 48 × 75 = 3600
So product of means = Product of extremes
Hence, 48, 60, 75 are in continued proportion.
Answer:
(c) 60
Ratio = 3:5
Let x be any number such that we have:
3x + 5x = 96
⇒ 8x = 96
⇒ x = 96 = 12
8
The numbers are:
3x = 3 â× 12 = 36
5x = 5 â× 12 = 60
The largest number = 60
Page No 161:
Question 10:
(c) 60
Ratio = 3:5
Let x be any number such that we have:
3x + 5x = 96
⇒ 8x = 96
⇒ x = 96 = 12
8
The numbers are:
3x = 3 â× 12 = 36
5x = 5 â× 12 = 60
The largest number = 60
Answer:
(b) 4 : 5
Speed of the car = Distance = 288 km = 72 km/hr
Time 4 hr
Speed of the train = Distance = 540 km = 90 km/hr
Time 6 hr
Ratio of their speeds = 72:90
where, 72 = 72 â÷ 18 = 4 (H.C.F. of 72 and 90 is 18.)
90 90 â÷ 18 5
Page No 161:
Question 11:
(b) 4 : 5
Speed of the car = Distance = 288 km = 72 km/hr
Time 4 hr
Speed of the train = Distance = 540 km = 90 km/hr
Time 6 hr
Ratio of their speeds = 72:90
where, 72 = 72 â÷ 18 = 4 (H.C.F. of 72 and 90 is 18.)
90 90 â÷ 18 5
Answer:
(c) 14
Let the 4th term be x, such that we have:
12:21::8:x
Now, we know:
Product of extremes = Product of means
12x = 21 × 8
x = 168 = 14
12
Page No 161:
Question 12:
(c) 14
Let the 4th term be x, such that we have:
12:21::8:x
Now, we know:
Product of extremes = Product of means
12x = 21 × 8
x = 168 = 14
12
Answer:
(d) 4 : 5
92:115
92 = 92 â÷ 23 = 4 (H.C.F. of 92 and 115 is 23)
115 115 â÷ 23 5
Page No 161:
Question 13:
(d) 4 : 5
92:115
92 = 92 â÷ 23 = 4 (H.C.F. of 92 and 115 is 23)
115 115 â÷ 23 5
Answer:
(a) 95
Given :
57:x::51:85
We know:
Product of means = Product of extremes
51x = 57 × 85
x = 4845 = 95
51
Page No 161:
Question 14:
(a) 95
Given :
57:x::51:85
We know:
Product of means = Product of extremes
51x = 57 × 85
x = 4845 = 95
51
Answer:
(c) 36
Given:
4:5::x:45
We know:
Product of mean = Product of extremes
5x = 4 â× 45
x = 180 = 36
5
Page No 161:
Question 15:
(c) 36
Given:
4:5::x:45
We know:
Product of mean = Product of extremes
5x = 4 â× 45
x = 180 = 36
5
Answer:
(b) b2 = ac
Given:
a, b, c are in proportion, such that we have:
a:b::b:c
Now, we know:
Product of means = Product of extremes
b â× b = a â× c
b2 = ac
Page No 161:
Question 16:
(b) b2 = ac
Given:
a, b, c are in proportion, such that we have:
a:b::b:c
Now, we know:
Product of means = Product of extremes
b â× b = a â× c
b2 = ac
Answer:
(b) 15 hrs
Time taken by 10 boys to dig a pitch = 12 hours
Time taken by 1 boy to dig a pitch = 12 × 10 = 120 hours (Less boys would take more hours.)
Time taken by 8 boys to dig a pitch = 120 = 15 hours
8
Page No 161:
Question 17:
(b) 15 hrs
Time taken by 10 boys to dig a pitch = 12 hours
Time taken by 1 boy to dig a pitch = 12 × 10 = 120 hours (Less boys would take more hours.)
Time taken by 8 boys to dig a pitch = 120 = 15 hours
8
Answer:
(b) 185 km
Distance covered by a car in 8 litres of petrol = 148 km
Distance covered by it in 1 litre of petrol = 148 km
8
Distance covered by it in 10 litres of petrol = 10 × 148 = 1480 = 185 km
8 8
Page No 161:
Question 18:
(b) 185 km
Distance covered by a car in 8 litres of petrol = 148 km
Distance covered by it in 1 litre of petrol = 148 km
8
Distance covered by it in 10 litres of petrol = 10 × 148 = 1480 = 185 km
8 8
Answer:
(i)
(ii) 90 cm:1.5 m (or) 90 cm:150 cm (1 m = 100 cm)
90 = 9 = 9 ÷ 3 = 3 (H.C.F. of 9 and 15 is 3.)
150 15 15 ââ÷ 3 5
(iii) If 36:81::x:63
Product of means = Product of extremes
81x = 36 × 63
x = 2268
81
x = 28
(iv) Given:
25, 35, x are in proportion.
25:35::35:x
Now, we know:
Product of extremes = Product of means
25 × x = 35 â× 35
25x = 1225
x = 1225 = 49
25
(v) Given:
9, x, x, 49 are in proportion.
9:x::x:49
Now, we know:
Product of means = Product of extremes
x â× x = 9 â× 49
x2 = 441
x2 = 212
x = 21
Page No 162:
Question 19:
(i)
(ii) 90 cm:1.5 m (or) 90 cm:150 cm (1 m = 100 cm)
90 = 9 = 9 ÷ 3 = 3 (H.C.F. of 9 and 15 is 3.)
150 15 15 ââ÷ 3 5
(iii) If 36:81::x:63
Product of means = Product of extremes
81x = 36 × 63
x = 2268
81
x = 28
(iv) Given:
25, 35, x are in proportion.
25:35::35:x
Now, we know:
Product of extremes = Product of means
25 × x = 35 â× 35
25x = 1225
x = 1225 = 49
25
(v) Given:
9, x, x, 49 are in proportion.
9:x::x:49
Now, we know:
Product of means = Product of extremes
x â× x = 9 â× 49
x2 = 441
x2 = 212
x = 21
Answer:
(i) 30, 40, 45, 60
30 = 3 , 45 = 45 â÷ 15 = 3 They are in proportion.
40 4 60 60 â÷ 15 4
Hence, true.
(ii) 6 = 6 â÷ 2 = 3 , 9 = 9 â÷ 3 = 3 Hence, they are equivalent to 3:4.
8 8 â÷ 2 4 2 12 â÷ 3 4
Hence, true.
(iii) 1 dozen:1 score = 12:20
12 = 12 â÷ 4 = 3
20 20 â÷ 4 5
Hence, false.
(iv) 60p:Rs 3 = 60p:300p (1 Re = 100 p)
60 = 6 = 6 â÷ 6 = 1
300 30 30 â÷ 6 5
Hence, true.
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