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Discussion :: Average

  1. Average age of a group of 30 boys is 16 years. A boy of age 19 leaves the group and a new boy joins the group. If the new average age of the group is 15.8 years, find the age of the new boy.
    2. A.
    12 years
    B.
    13 years
    C.
    14 years
    D.
    15 years

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    Answer : Option B

    Explanation :

    Let the age of new boy = X years

    Total age of 30 boys = 30*16 = 480 years

    As per question, if we minus age of boy who leaves the group and then add the age of boy who joins the group the new average becomes = 15.8 years.

    ∴ Apti Average 21 = 15.8

    480 - 19 + X = 474

    X = 474 - 480 +19

    X = - 6 +19

    = 13 years

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