The average age of 30 students is 9 years. If the age of their teacher is included, the average age becomes 10 years. The age of the teacher (in years) is :

A. 27

B. 31

C. 35

D. 40

Answer: Option D

Solution(By Examveda Team)

Let the age of teacher = x years
According to the question,
30 × 9 + x = 31 × 10
270 + x = 310
x = 40 years