The following table shows the number of working hours and the number of employees employed in a small scale industry

No. of working hours	No. of employees
3 - 5	7
5 - 7	10
7 - 9	18
9 - 11	57
11 - 13	14
13 - 15	8

The average number of working hours of an employee is

A. 8.5

B. 9.5

C. 10.5

D. None of these

Answer: Option B

Solution(By Examveda Team)

We have :

Mean working hours	4	6	8	10	12	14
No. of employees	7	10	18	57	14	8

Sum of working hours of all the employees
= (4 × 7 + 6 × 10 + 8 × 18 + 10 × 57 + 12 × 14 + 14 × 8)
= (28 + 60 + 144 + 570 + 168 + 112)
= 1082
Total number of employees
= (7 + 10 + 18 + 57 + 14 + 8)
= 114
∴ Average number of working hours
= $$\left( {\frac{{1082}}{{114}}} \right)$$
= 9.49 $$ \approx $$ 9.5