Multiple choice

The average age of 20 students in a class is 15 years. If the teacher's age is included, the average increases by one, then what is the teacher's age?

  1. 30 years

  2. 21 years

  3. 42 years

  4. 36 years
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total age of 20 students = 20 * 15 = 300. With teacher, total people = 21, average = 16. New total = 21 * 16 = 336. Teacher's age = 336 - 300 = 36.

AI explanation

The total age of the 20 students is 20 times 15 years, which equals 300 years. When the teacher is included, there are 21 people with an average age of 16 years, making the new total age 21 times 16, which equals 336 years. The teacher's age is the difference between the new total and the old total, so 336 minus 300 equals 36 years.

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