Multiple choice

The average weight of 21 boys is 68 kgs. If the teacher's weight is included, the average weight is increased by 1 kg. What is the teacher's weight?

  1. $86 kgs.$
  2. $64 kgs.$
  3. $72 kgs.$
  4. $92 kgs.$
  5. $90 kgs.$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Total weight of 21 boys = 21 × 68 = 1428 kg. When teacher is included, total people = 22, new average = 69 kg. New total weight = 22 × 69 = 1518 kg. Teacher's weight = 1518 - 1428 = 90 kg. Alternatively, use the shortcut: teacher's weight = new average + (number of boys × increase) = 69 + 21 = 90 kg.

Keep practicing — related questions