Multiple choice

The average age of $24$ boys and a teacher is $15$ . When the teacher' age is excluded the average decreases by $ 1$. What is the age of the teacher?

  1. $39$ years
  2. $38$ years
  3. $40$ years
  4. $41$  years
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A Correct answer
Explanation

Total age of 24 boys and teacher = 25 * 15 = 375. Total age of 24 boys = 24 * 14 = 336. Teacher's age = 375 - 336 = 39.

AI explanation

Using the formula for averages, the total age of the 24 boys and the teacher is 25 times 15 = 375 years. When the teacher's age is excluded, the average drops by 1 year, making the new average 14 years. The total age of the 24 boys is 24 times 14 = 336 years, so the teacher's age is 375 minus 336, which equals 39 years. The age of the teacher is 39 years.

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