There are 20 students in a class. If the average age of the students is 20 years including the age of the teacher and reduces by 10% when the age of the teacher is removed, find the age of the teacher.

There are 20 students in a class. If the average age of the students is 20 years including the age of the teacher and reduces by 10% when the age of the teacher is removed, find the age of the teacher. Correct Answer 60 years

The average age of the class including the age of the teacher = 20 * 21 (20 students and 1 Teacher makes 21) 20 * 21 = 420 The average without the age of teacher = 20 – 10% of 20 = 20 – 10 * 20 / 100 = 20 – 2 = 18 year Average age of 20 boys = 18 years Total age of 20 boys = 20 * 18 = 360 years Age of the teacher = 420 – 360 = 60 years
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