Question

the table shows the marks obtained by 20 students In a class test in geography out of a total of 20 marks marks obtained is 12,15 16,19,x,9 and number of students 2,5,3,4,2,4 . if the mean of the marks obtained is 14,find x.​

Answer 1

Marks (xi) Frequency (fi) (fi×xi)

12 2 24

15 5 75

16 3 48

19 4 76

2 x 2x

9 4 36

sigma (fi)=(18+x) sigma (fi×xi)=(259+2x)

• Mean = sigma (fi×xi)/sigma (fi)

14 = (259 + 2x)/(18 + x)

(252+14x) = (259 + 2x)

x = 259 - 252

x = 7