1.  10 years ago, the average age of a family of 4 members was 24 years. Two children having been born (with age different of 2 years), the present average age of the family is the same. The present age of the youngest child is :
A. 1 year
B. 2 years
C. 3 years
D. 5 years

Answer: Option

Explanation:

Total age of 4 members, 10 years ago
= (24 x 4) years
= 96 years

Total age of 4 members now = (96 + 10 x 4) years
= 136 years.

Total age of 6 members now = (24 x 6) = 144 years.
Sum of the ages of 2 children = (144 - 136) years
= 8 years.

Let the age of the younger child be X years.

Then, age of the elder child = (X + 2) years.
So X + X + 2 = 8 <=> 2X = 6
<=> X = 3

Age of younger child = 3 years.