# Find out The Age of The Youngest Boy.

The average age of 3 boys is 30 years and the ratio of their ages is 3: 5: 7. Find out the age of the youngest boy.

- 16 years
- 12 years
- 15 years
- 18 years

**Answer: (4) 18 years**

**Explanation:-
**The average age of 3 boys = 30 years

Then, the sum of the age of 3 boys = 3 x 30 = 90 years

The ratio of their age = 3: 5: 7.

Let the age of their be 3X, 5X and 7X.

Then, 3X + 5X + 7X = 90

15 X = 90

X = 90/15

X = 6

Then, the age of youngest boy is 3X = 3 x 6 = 18 years.

Hence, the answer is (4) 18 years.