# The age of the new boy is :

In a class there are 30 boys and their average age is 17 years. On one boy aged 18 years leaving the class and another joining, the average age becomes 16.9 years. The age of the new boy is

- 11 years
- 13 years
- 15 years
- 25 years

**Answer is 15 years**

**Explanation:-**

The average age of 30 boys in a class = 17 years

On one boy aged 18 years leaving the class and another joining, the average age becomes 16.9 years.

Then, the age of new boy = 18 – (17 – 16.0) x 30

= 18 – 0.1 x 30

= 18 – 3

= 15 years

Then, the age of new boy is 15 years.

Hence, the correct answer is option (1) 15 years.