• Numerical Ability - Problems on Ages
Question

The average age of  30 students is  9  years. If  the age of their  teacher  is included,  it becomes 10 years. The age of the teacher is

  • A) 27 years
  • B) 31 years
  • C) 35 years
  • D) 40 years
  • E) None of These
Solution

Answer: Option D

Explanation :

Given 30 students avg. age = 9 years.
So total age of 30 students = 9*30 = 270 years.
Teacher's age included. 
So, avg. of 30 students + one teacher = 10 years.
=> Total age of 30 students + one teacher = 10 * 31 = 310 years. 
Therefore age of teacher = (310-270) = 40 years.

Answer: Option D

Explanation :

Given 30 students avg. age = 9 years.
So total age of 30 students = 9*30 = 270 years.
Teacher's age included. 
So, avg. of 30 students + one teacher = 10 years.
=> Total age of 30 students + one teacher = 10 * 31 = 310 years. 
Therefore age of teacher = (310-270) = 40 years.
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