### In a class, there are 40 boys and their average age is 16 years. One boy, aged 17 years, leaving the class and another joining, the average age becomes 15.875 years The age of the new boy is :

A. 12 years B. 14.5 years C. 15 years D. 17 years Answer: Option A

### Solution(By Apex Team)

$\begin{array}{l}\text{Sum of age of 40 boys}\\ \text{= 16 × 40 = 640}\\ \text{New age of 40 boys}\\ \text{= 15.875 × 40 = 635}\\ \text{Difference = (640 – 635)}\\ =5\ \text{years}\\ \text{17 – x = 5}\\ \text{x = 17 – 5 = 12 years}\end{array}$

A. 20
B. 21
C. 28
D. 32

A. 18
B. 20
C. 24
D. 30

A. 10 years
B. 10.5 years
C. 11 years
D. 12 years