The average of 10 students is 13 years, if the teacher's age is included, the average increases by two. The age of the teacher is -

Question: The average of 10 students is 13 years, if the teacher's age is included, the average increases by two. The age of the teacher is -

Solution:
Average of 10 students = 13 years
Total age of 10 students
= 10 × 13
= 130 years
When teacher included average become 15 years
Now, total age 10 students and teacher
= 15 × 11 = 165 years
∴ Age of teacher
= 165 - 130
= 35 years