The average age of a class of 39 students is 15 years. If the age of the teacher be included, then the average increases by 3 months. Find the age of the teacher.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e 25 years.
Average age of 39 students = 15 years
Including teacher, average increases by 3 months = 0.25 years
New average = 15 + 0.25 = 15.25 years
Total people = 39 students + 1 teacher = 40
Total age of 39 students = 39 × 15 = 585 years
Total age of 40 people = 40 × 15.25 = 610 years
Age of the teacher = Total age of 40 people - Total age of 39 students = 610 - 585 = 25 years