Question

The average age of 60 students in a class is 18 years. The average age of a group of 25 boys is 20 years and the average age of a group of 25 girls is 17 years. What is the average age of remaining students of the class? 
1. 15.5 years
2. 14.5 years
3. 16.5 years
4. 15 years
5. 12 years

Answer 1

Correct Answer - Option 1 : 15.5 years

Given:

Average age of 60 students = 18 years

Average age of 25 boys = 20 years

Average age of 25 girls = 17 years

Formula used:

Average = sum of observations/total number of observations

Calculation:

Total age of the class = 18 × 60 = 1080 years

Total age of 25 boys = 25 × 20 = 500 years

Total age of 25 girls = 25 × 17 = 425 years

Age of remaining 10 students = 1080 - (500 + 425) = 155

Average age = 155/10 = 15.5 years

∴ The average age is 15.5 years