Question

The following frequency distribution table shows the amount of aid given to 50 flood affected families. Find the mean of the amount of aid.

Amount of aid (Thosand rupees)	50 - 60	60 - 70	70 - 80	80 - 90	90 - 100
No. of families	7	13	20	6	4

Answer 1

Class (Amount of aid in thousand rupees)	Class Mark xi	Frequency (Number of families) fi	Class mark × Frequency xifi
50 - 60	55	7	385
60 - 70	65	13	845
70 - 80	75	20	1500
80 - 90	85	6	510
90 - 100	95	4	380
		$\sum _{}{f}_i=50$	$\sum _{}{x}_i{f}_i=3620$

Mean = $\frac{\sum _{}{x}_i{f}_i}{\sum _{}{f}_i}$
​$$\begin{gathered} =\frac{3620}{50} \\ =72.4\mathrm{thousand}\mathrm{rupees} \\ =\mathrm{Rs}72400 \end{gathered}$$
Hence, the mean of the amount of acid is Rs 72400.