Multiple choice

The average age of 20 students in a class is 21. If the age of the teacher is included, the average age increases by 2 years. Find the age of the teacher?

  1. 60yr

  2. 63yr

  3. 66yr

  4. 61yr

  5. None of these

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

The total age of 20 students is 20 × 21 = 420 years. When the teacher joins, there are 21 people with average age 23, so total becomes 21 × 23 = 483 years. The teacher's age is the difference: 483 - 420 = 63 years.