Mathematics Solutions Solutions for Class 8 Math Chapter 17 Surface Area And Volume are provided here with simple step-by-step explanations. These solutions for Surface Area And Volume are extremely popular among Class 8 students for Math Surface Area And Volume Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Mathematics Solutions Book of Class 8 Math Chapter 17 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Mathematics Solutions Solutions. All Mathematics Solutions Solutions for class Class 8 Math are prepared by experts and are 100% accurate.

Page No 108:

Question 1:

Find the volume of a box if its length, breadth and height are 20 cm, 10.5 cm and 8 cm respectively.

Answer:

Volume of the box=length×breadth×height                                =20×10.5×8                                =1680 cm2

Page No 108:

Question 2:

A cuboid shape soap bar has volume 150 cc. Find its thickness if its length is 10 cm and breadth is 5 cm.

Answer:

Volume of soap bar = 150 cc
lbh=15010×5×h=150h=15010×5=3 cm

Page No 108:

Question 3:

How many bricks of length 25 cm, breadth 15 cm and height 10 cm are required to build a wall of length 6 m, height 2.5 m and breadth 0.5 m?

Answer:

Let the number of bricks required be n. 
Volume of each brick = 25×15×10=3750 cm3
Volume of the wall = 6×2.5×0.5=7.5 m3
Number of bricks required(n) = Vol of wallVol of brick=7.5×10000003750=2000
Thus, 2000 bricks are required to make the wall.



Page No 109:

Question 4:

For rain water harvesting a tank of length 10 m, breadth 6 m and depth 3 m is built. What is the capacity of the tank? How many litre of water can it hold?

Answer:

length = 10 m
breadth = 6 m
depth = 3 m 
Volume of the tank = 10×6×3=180 m3
1 m3=1000L180 m3=180000L



Page No 110:

Question 1:

In each example given below, radius of base of a cylinder and its height are given. Then find the curved surface area and total surface area.
(1) r = 7 cm, h = 10 cm
(2) r = 1.4 cm, h = 2.1 cm
(3) r = 2.5 cm, h = 7 cm
(4) r = 70 cm, h = 1.4 cm
(5) r = 4.2 cm, h = 14 cm

Answer:

We know that
Curved surface area of a cylinder = 2πrh
Total surface area = 2πrh+r
(1) r = 7 cm, h = 10 cm
Curved surface area of a cylinder = 2πrh = 2π×7×10=140π=140×227=440 sq cm
Total surface area = 2πrh+r = 2×227×710+7=748 sq cm
(2) r = 1.4 cm, h = 2.1 cm
Curved surface area of a cylinder = 2πrh = 2×227×1.4×2.1=18.48 sq cm
Total surface area = 2πrh+r = 2×227×1.42.1+1.4=30.8 sq cm
(3) r = 2.5 cm, h = 7 cm
Curved surface area of a cylinder = 2πrh = 2×227×2.5×7=110 sq cm
Total surface area = 2πrh+r = 2×227×2.52.5+7=149.28 sq cm
(4) r = 70 cm, h = 1.4 cm
Curved surface area of a cylinder = 2πrh = 2×227×70×1.4=616 sq cm
Total surface area = 2πrh+r = 2×227×7070+1.4=31416 sq cm
(5) r = 4.2 cm, h = 14 cm
Curved surface area of a cylinder = 2πrh = 2×227×4.2×14=369.6 sq cm
Total surface area = 2πrh+r = 2×227×4.24.2+14=480.48 sq cm
 

Page No 110:

Question 2:

Find the total surface area of a closed cylindrical drum if its diameter is 50 cm and height is 45 cm. (π = 3.14)

Answer:

Diameter = 50 cm
Radius = 25 cm
Height = 45 cm
Total surface area = 2πrh+r
=2×3.14×2525+45=10990 sq cm
Thus, the total surface area of the closed cylinderical drum is 10990 sq cm.



Page No 111:

Question 3:

Find the area of base and radius of a cylinder if its curved surface area is 660 sqcm and height is 21 cm.

Answer:

Curves surface area = 660 sq cm
Height = 21 cm
Curved surface area = 2πrh=2×227×r×21=660
132r=660r=660132=5 cm
Area of base = πr2=227×52=78.57 sq cm

Page No 111:

Question 4:

Find the area of the sheet required to make a cylindrical container which is open at one side and whose diameter is 28 cm and height is 20 cm. Find the approximate area of the sheet required to make a lid of height 2 cm for this container.

Answer:

Diameter = 28 cm
Radius = 14 cm
Height = 20 cm
Curved surface area of the cylinder + area of the base = area of the sheet 
Area of sheet=2πrh+πr2Area of sheet=πr2h+rArea of sheet=227×142×20+14Area of sheet=2376
Thus, area of sheet required = 2376 cm
Area of sheet required to make a lid of height 2 cm will be
Area of sheet=2πrh+πr2=πr2h+r=227×142×2+14=44×18=792
Thus, area of sheet used to make the lid is 792 sq cm.



Page No 112:

Question 1:

Find the volume of the cylinder if height (h) and radius of the base (r) are as given below.
(1) r = 10.5 cm, h =8 cm
(2) r = 2.5 m, h = 7 m
(3) r = 4.2 cm, h = 5 cm
(4) r = 5.6 cm, h = 5 cm

Answer:

Volume of the cylinder = πr2h
(1) r = 10.5 cm, h =8 cm
Volume = πr2h227×10.5×10.5×8=2772 cubic cm
(2) r = 2.5 m, h = 7 m
Volume = πr2h = 227×2.5×2.5×7=137.5 cubic cm
(3) r = 4.2 cm, h = 5 cm
Volume = πr2h = 227×4.2×4.2×5=277.2 cubic cm
(4) r = 5.6 cm, h = 5 cm
Volume = πr2h = 227×5.6×5.6×5=492.8 cubic cm
 

Page No 112:

Question 2:

How much iron is needed to make a rod of length 90 cm and diameter 1.4 cm?

Answer:

Total length = 90 cm
Diameter = 1.4 cm
Radius = 0.7 cm
Total iron required = Volume of cylinder 
πr2h=227×0.7×0.7×90=138.6 cm
Thus, 138.6 cmof iron is required.

Page No 112:

Question 3:

How much water will a tank hold if the interior diameter of the tank is 1.6 m and its depth is 0.7 m?

Answer:

Diameter = 1.6 m
Radius = 0.8 m
Depth = 0.7 m
Volume of the tank = πr2h=227×0.82×0.7=1.408 m3.
1 m3=1000 L1.408 m3=1.408×1000=1408 L
Thus, the tank will hold 1408 L.



 

Page No 112:

Question 4:

Find the volume of the cylinder if the circumference of the cylinder is 132 cm and height is 25 cm.

Answer:

Circumference = 132 cm
2πr=1322×227r=132r=132×72×22=21 cm
Height = 25 cm
Volume = πr2h=227×21×21×25=34650 cm3
 



View NCERT Solutions for all chapters of Class 8