Multiple choice

The average age of 30 girls and their teacher is 16. If the teacher's age is removed, then the average decreases by 1. What is the teacher's age?

  1. 46

  2. 36

  3. 31

  4. 45

  5. 48
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A Correct answer
Explanation

Total age of 31 people (30 girls + teacher) = 31 × 16 = 496 years. Average of 30 girls alone = 16 - 1 = 15 years, so their total age = 30 × 15 = 450 years. Teacher's age = 496 - 450 = 46 years.

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