Question

The table below shows children in a class sorted according to their weights.

Weight (kg)	Number of children
21 – 23	4
23 – 25	—
25 – 27	7
27 – 29	6
29 – 31	3
31 – 33	1

The mean weight is calculated as 26 kilograms. How many children have weights between 23 and 25 kilograms?

Answer 1

Let’s prepare the table for finding the mean by considering the number of children in the group 23 to 25, as ‘x’.

Weight (kg)	No. of children	Mid value	Total weight
21 – 23	4	22	22 × 4 = 88
23 – 25	X	24	24 × x = 24x
25 – 27	7	26	26 × 7 = 182
27 – 29	6	28	28 × 6 = 168
29 – 31	3	30	30 × 3 = 90
31 – 33	1	32	32 × 1 = 32
Total	21 + x		560 + 24x

Mean weight = 26 kg

i.e; the number of children having weight between 23 to 25 is 7.