Multiple choice

The average age of 41 students of a class is 15 years. When one boy leaves the class, the average is reduced by 0.05 year. Find the age of the boy who left the class.

  1. 13 years

  2. 14 years

  3. 17 years

  4. 16 years

  5. 15 years

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Original average age (A) = 15 years

Original number of students (N) = 41

Difference in average ages (d) = 0.05 years

Now, apply the shortcut formula:

Age of the boy who left the class = A - (1 - N)d 

= 15 - (1 - 41) * 0.05 

= 17 years 

So, the age of the boy who left the class was 17 years.