in a class test ,marks obtained by 120 students are given in the following frequency distribution the mean is 69 - Maths - Statistics

Question

in a class test ,marks obtained by 120 students are given in the
following frequency distribution the mean is 69 find x and y
C I F I
0-10 1
10-20 3
20-30 7
30-40 10
40-50 15
50-60 X
60-70 9
70-80 27
80-90 18
90-100 Y

Vijay Kumar Gupta · Accepted Answer

Dear student,

Please find below the solution to the asked query:

Consider the following table
<img alt="" src=
"https://s3mn%20mnimgs%20com/img/shared/ck-files/ck_56249cd4e51c0%20png"
style="width: 300px; height: 136px;">

Since there are total 120 students
 This gives,    90+x+y=120          x+y=30             
1Also, we have mean=69
 This gives              A+∑i fiui∑i fi×h=69    45+134+x+5y120×10=69           45+134+x+5y12=69        540+134+x+5y12=69                   674+x+5y12=69×12                     674+x+5y=828                                x+5y=154      
2Subtract 1  from 2  to get,     x+5y=154       x+y=30    -  -     -              4y=124            y=31This cannot be possible as x=-1 when we use y=31There is something wrong with the question or may be the given value of mean is not correct

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in a class test ,marks obtained by 120 students are given in the following frequency distribution the mean is 69 find x and y C.I F.I 0-10 1 10-20 3 20-30 7 30-40 10 40-50 15 50-60 X 60-70 9 70-80 27 80-90 18 90-100 Y

in a class test ,marks obtained by 120 students are given in the following frequency distribution the mean is 69 find x and y
C.I F.I
0-10 1
10-20 3
20-30 7
30-40 10
40-50 15
50-60 X
60-70 9
70-80 27
80-90 18
90-100 Y