Multiple choice general knowledge math & puzzles

The avg. age of 30 boys of a class is 14 years. When the age of the class teacher is included, the average becomes 15 years. Find the age of class teacher?

  1. 40

  2. 39

  3. 45

  4. 42

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total age of 30 boys = 30 × 14 = 420 years. When teacher is included, 31 people have average 15, so total = 31 × 15 = 465 years. Teacher's age = 465 - 420 = 45 years. This is a standard average problem where you work backwards from totals.