Question

Choose the correct answers from the alternatives given.
The average age of three boys is 15 years. If their ages are in the ratio of 3 :5 :7. then the age of the youngest boy (in years) is

• A. 15
• B. 18
• C. 21
• D. 9

Answer 1

The correct option is D 9

Total age of the three boys 15 $\ast$ 3 = 45 years.

Let the ratio be $x$

$\therefore 3x+5x+7x=15x=45$
$x$ = $3years.$
Hence. the age of youngest boy is $9years$.