Three boys, on average, are 25 years old, and their ages are in the ratio of 3 : 5 : 7. What is the age of the youngest boy?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 15 years.
Given that,
The ages of the three boys are in the ratio of 3 : 5 : 7
Let the ages of these boys be 3x, 5x, 7x, respectively
The average age of them = 25 years
The sum of their age = Average × number of boys
Sum = 25 × 3 = 75 years
According to the question
⇒ 3x + 5x + 7x = 75
⇒ 15x = 75
⇒ x = 75/15 = 5
Hence, the age of the youngest boy = 3x = 3 × 5 = 15 years