Question 108

Out of 10 teachers of a school, one teacher retires and in his place, a new teacher of age 25 years joins. As a result, average age of teachers is reduced by 3 years. The age (in years) of the retired teacher is:

Solution

Number of teachers = 10 years

Let the initial average age be A years

total age before retirement = 10A

Now new average age =( A-3) years

So new total age after new person joined= 10x(A-3) = 10A - 30 .............(1)

let the age of retired teacher be z years, So

new total age can be calculated also as= 10A - z +25 ........(2)

equations 1 and 2 are equal

so, 10A - 30 = 10A - z +25

z = 55 years.

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