The age of the new boy is :

In a class there are 30 boys and their average age is 17 years. On one boy aged 18 years leaving the class and another joining, the average age becomes 16.9 years. The age of the new boy is

  1. 11 years
  2. 13 years
  3. 15 years
  4. 25 years
Anurag Mishra Professor Asked on 29th December 2015 in Maths.
Add Comment
  • 1 Answer(s)

    Answer is 15 years

    Explanation:-
    The average age of 30 boys in a  class = 17 years

    On one boy aged 18 years leaving the class and another joining, the average age becomes 16.9 years.
    Then,  the age of new boy = 18 – (17 – 16.0) x 30 
     = 18 – 0.1 x 30
     = 18 – 3
     = 15 years

    Then, the age of new boy is 15 years. 

    Hence, the correct answer is option (1) 15 years.  

    Monis Rasool Professor Answered on 29th December 2015.
    Add Comment
  • Your Answer

    By posting your answer, you agree to the privacy policy and terms of service.