Question

The average age of 40 students of a class is 12 years. If the age of the teacher is also included, the average age of the whole group becomes 13 years. The age (in years) of the teacher is:

• A. 50
• B. 51
• C. 53
• D. 56

Answer 1

Answer:

C. 53

Number of students = 40
Average age = 12

Total age of students

$40 \times 12 = 480$
Now including teacher:
Total people = 41
New average = 13

Total age including teacher

$41 \times 13 = 533$
Age of teacher

533 - 480 = 53

= 53 years