The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?
Q1. The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?
Answer: 9
Explanation: Total age of three boys = 3 × 15 = 45; ratio 3:5:7 sums to 15 parts; youngest's age = (3/15) × 45 = 9 years.