Question

The average age of 21 boys is 29 years. When one boy leaves the average age increased by 1/4 year. How old is the boy who leaves?

Answer 1

Answer:

24

Step-by-step explanation:

Original total age = 21*29 = 609 Yrs.

New total age = 20*29.25 = 585 Yrs.

The age of boy who left = 609 - 585 = 24

Answer 2

Answer:

The boy who leaves is 24 years old.

Step-by-step explanation:

Given that the average age of 21 boys is 29 years. Then the total age of 21 boys is

= 29 × 21 years = 609 years

Also given that the after the boy leaves, the average age of (21 - 1) = 20 boys increases by 1/4 year.

Then total age of 20 boys is

= 20 × {29 + 1/4) years

= 20 × (29 + 0.25) years

= 20 × 29.25 years

= 585 years

Therefore the age of the boy who leaves is

= total age of 21 boys - total age of 20 boys

= (609 - 585) years

= 24 years