The ages of students in a small primary school were recorded in the table below.

 Age                   5 - 6              7 - 8        9 -10
Frequency           29               40          38 


Estimate the mean

A.

7.7

B.

7.5

C.

7.8

D.

7.6

Correct answer is A

Class Interval          Class Mark          Frequency (f)               fx       
        5 - 6              5.5                29 5.5 x 29 = 159.5
        7 - 8              7.5                40 7.5 x 40 = 300
       9 - 10              9.5                38 9.5 x 38 = 361
    \(\sum f = 107\) \(\sum fx = 820.5\)


Mean = \(\frac{\sum fx}{\sum f} = \frac {820.5}{107}\) = 7.7 (1 d.p)