Question

The average age of three boys is 16 years and the ratio of their ages is 4 : 5 : 7, find out the age of smallest boy.
1. 8 years
2. 9 years
3. 12 years
4. 16 years

Answer 1

Correct Answer - Option 3 : 12 years

Given: 

The average age of three boys is 16 years and the ratio of the three boys is 4 : 5 : 7

Concept: 

Average = (Sum of all observation/Number of observation)

Calculation: 

Let the age of the three boys is 4x, 5x, and 7x 

Now, 

The average of three boys is 

⇒ (4x + 5x + 7x)/3

⇒ 16x/3

According to the question,

⇒ 16x/3 = 16

⇒ x = 16 × 3/16

⇒ x = 3

The age of the smallest boy is 

⇒ 4x

⇒ 4 × 3

⇒ 12 years  

∴ The age of the smallest boy is 12 years.