Multiple choice

The average age of a group of 10 students is 12 years. If a teacher joins the group, the average age increases by 1 year. If another teacher of the same age also joins the group, what will be the average age of the whole group?

  1. 11 years

  2. 12.93 years

  3. 13 years

  4. 13.83 years

  5. 14 years
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Initial: 10 students, avg 12, sum 120. Teacher 1 joins: 11 people, avg 13, sum 143. Teacher 1 age = 143 - 120 = 23. Teacher 2 (same age) joins: 12 people, sum 143 + 23 = 166. New average = 166 / 12 = 13.833.

AI explanation

The total age of the initial 10 students is 10 multiplied by 12, which equals 120 years. The first teacher increases the total age to 11 multiplied by 13, equaling 143 years, meaning the teacher is 23 years old. When a second 23-year-old teacher joins, the new total age becomes 143 + 23 = 166 years. The average age for the 12 people is then 166 divided by 12, which equals 13.83 years.

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