Question 137

In a class there are 30 boys and their average age is 17 years. If one boy aged 18 years leaves and other joins the class, then average age becomes 16.9 years. The age of the new boy is

Solution

Total age of 30 boys = 30 x 17 = 510

If one boy aged 18 years leaves, then total age will be (510 - 18) = 492

Total age after the new boy joins the class = 16.9 x 30 = 507

$$\therefore$$ Age of the new boy = 507 - 492 = 15 years

Hence, option B is the correct answer.

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