Multiple choice

The average age of 10 students is 12 years. If the age of a teacher is added to the age of the students, then the average age increases by 1. If the age of another teacher, as old as the first teacher, is included, then what will be the average age of all the 10 students and 2 teachers together (in years)?

  1. 13

  2. 14

  3. 14.83

  4. 13.83

  5. 15
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sum of 10 students = 120. Teacher 1 added: (120 + T) / 11 = 13. 120 + T = 143, T = 23. Two teachers added: (120 + 23 + 23) / 12 = 166 / 12 = 13.833.

AI explanation

The initial total age for the 10 students is 10 multiplied by 12, giving 120 years. Including the first teacher makes the total 11 multiplied by 13, which is 143, so the teacher is 23 years old; adding a second 23-year-old teacher brings the new total age to 166. Dividing this new total age of 166 by the 12 people gives a final average age of 13.83 years.

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