Question

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)?

• A. 45
• B. 60
• C. 55
• D. 50

Answer 1

Answer:

B. 60

Number of students = 35
Average age = 15

Total age of students

$35 \times 15 = 525$
Average increases by 1.25 ⇒ New average =
15 + 1.25 = 16.25
Total people = 36

Total age including teacher

$36 \times 16.25 = 585$
Teacher’s age

585 - 525 = 60

=60 years