The average age of a class of 39 students is 20 years. If the age of the teacher is included, then the average increases by 6 months. Find the age of the teacher (in years).
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 40.
Number of students = 39
Average age of students = 20 years
New average including teacher = 20 + 0.5 = 20.5 years
Total people now = 40
Total age of students = 39 × 20 = 780 years
Total age including teacher = 40 × 20.5 = 820 years
Age of teacher = 820 − 780 = 40 years