The following distribution shows the daily pocket allowance of children of a locality. The mean poc

The following distribution shows the daily pocket allowance of children of a locality. The mean pocket allowance is Rs 18. Find the missing frequency f.

Daily pocket allowance (in 3)

Number of children

11-13

7

13-15

6

15-17

9

17-19

13

19-21

f

21-23

5

23-25

4