Question

Find the mean marks from the following data:

Marks	No. of students
Below $10$	$4$
Below $20$	$10$
Below $30$	$18$
Below $40$	$28$
Below $50$	$40$
Below $60$	$70$

• A. $40\frac{5}{7}marks$
• B. $40\frac{4}{7}marks$
• C. $30\frac{5}{7}marks$
• D. $20\frac{4}{7}marks$

Answer 1

The correct option is A $40\frac{5}{7}marks$

For the grouped data, when class interval is given we find class marks by using the formula

Class mark$\left(x_i\right)=\frac{(Lowerlimit+Upperlimit)}{2}$

Find $x_i{f}_i$ and then

Mean $=\frac{\sum x_i{f}_i}{\sum f_i}=\frac{2850}{70}=\frac{285}{7}=40\frac{5}{7}$ marks