The average age of 24 students in a class is 15 years. When the teacher's age is included, the average increases by 1. What is the teacher's age (in years)?
Answer & explanation
Correct answer: option 4
Total age of 24 students = 24 × 15 = 360 years
Total age of 24 students & 1 teacher = ( 24 + 1 ) × 16 = 25 × 16 = 400 years
Age of teacher = 400 - 360 = 40 years