The average age of a teacher and three students in 20 years

The average age of a teacher and three students in 20 years. If all the three students are of same age and the difference between the age of the teachers and each student is 20 years, then what is the age of the teacher?

1. 25 years
2. 30 years
3. 35 years
4. 45 years

Answer: C

Explanation

Let the age of each student be x years and the age of the teacher be y years.

According to the question,

3x + y = 20 × 4

Or 3x + y = 80 (1)

Also, y – x = 20 (2)

By subtracting equation (1) by (2), we get:

4x = 60

Or x = 15 years

So, y = x + 20 = 15 + 20 = 35 years

• Exam Year: 2020