The average age of 17 boys and their teacher is 16 years When the teacher's age is excluded, the average age decreases by 1 year. The age of the teacher is:
Answer & explanation
Correct answer: option 4
The average age of 17 boys and their teacher = 16 years.
Total age of 17 boys and teacher = (17 + 1) × 16
When the teacher’s age is excluded, Total decreased age = 17 × (16 – 1)
The age of the teacher = (17 + 1) × 16 – 17 × (16 – 1)
∴ The age of the teacher = 18 × 16 – 17 × 15 = 288 – 255 = 33 years.