Question

The distribution of money collected by students for a flood relief fund is shown.

Money (in Rs.)	0-10	10-20	20-30	30-40	40-50
No. of students	5	7	5	2	6

Using the direct method, find the mean amount collected by a student.

Answer 1

Money (in Rs) (Class interval)	Class Marks $\left(x_i\right)$	No. of students $\left(f_i\right)$	$\left(f_i\right)$$\left(x_i\right)$
0-10	5	5	25
10-20	15	7	105
20-30	25	5	125
30-40	35	2	70
40-50	45	6	270
Total	-	$\sum _{}^{}{f}_i=25$	$\sum _{}^{}{f}_i{x}_i=59$5

$\mathrm{Mean}=\overline{x}=\frac{{\displaystyle \sum _{}^{}}{f}_i{x}_i}{{\displaystyle \sum _{}^{}}{f}_i}=\frac{595}{25}=\mathrm{Rs}23.80$

Therefore, the mean amount collected by a student is Rs 23.80.