Multiple choice

A class has 20 boys and 30 girls. The average age of boys is 11 years and that of girls is 12 years. What is the average age of the whole class?

  1. $11.6 years$
  2. $12 years$
  3. $11.2 years$
  4. $10 years$
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A Correct answer
Explanation

Total age of boys = 20 × 11 = 220 years. Total age of girls = 30 × 12 = 360 years. Combined total age = 580 years. Total students = 50. Average = 580 ÷ 50 = 11.6 years. This is a weighted average problem where the weights are the number of boys and girls.

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