The average age of 35 students in a group is 15 years. When the teacher's age is included, the average age of the group increases by 1.25 years. What is the teacher's age (in years)?

Correct option is B

Given:
Average age of 35 students = 15 years.
When the teacher's age is included, the average age of the group increases by 1.25 years
Formula Used: ​
Total sum = Average × Number of terms
Solution: ​
Total age of 35 students = 35 × 15 = 525 years
New Average = 15+ 1.25 = 16.25 Years
Total age of whole class when teacher is also included = 36 × 16.25 = 585 years
Teacher's age = 585- 525 = 60 years