The average age of 57 students of a class is 13 years. If the age of the teacher is also included, the average age of the whole group becomes 14 years. The age (in years) of the teacher is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 71.
Total age of 57 students = 57 × 13 = 741
Total people = 58, new average = 14 → total age = 58 × 14 = 812
Teacher’s age = 812 - 741 = 71 years