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Average Age of New Entrants

MAT 2018 · Mathematical Skills · Easy · Arithmetic

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The average age of 40 boys of a class is 12 years. When 10 new boys are admitted, the average is increased by 0.1 year. What is the average age of new boys?

  1. A.

    12.1 years

  2. B.

    12.4 years

  3. C.

    12.33 years

  4. D.

    12.5 years

Answer

D

Explanation

Total age of 40 boys = 40×12=48040 \times 12 = 480 years.

When 10 new boys join, total students = 50, and new average = 12+0.1=12.112 + 0.1 = 12.1 years. Total age of 50 boys = 50×12.1=60550 \times 12.1 = 605 years.

Sum of ages of 10 new boys = 605−480=125605 - 480 = 125 years.

Average age of new boys = 12510=12.5\frac{125}{10} = 12.5 years.

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