The mean age of a combined group of men and women is 25 yrs. If the mean age of the group of men is 26 and that of the group of women is 21, then the percentage of men and women in the group is

The mean age of a combined group of men and women is 25 yrs. If the mean age of the group of men is 26 and that of the group of women is 21, then the percentage of men and women in the group is

  1. A

    60, 40

  2. B

    80, 20

  3. C

    20, 80

  4. D

    40, 60

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    Solution:

    The formula for combined mean is

    X¯=n1X¯1+n2X¯2n1+n2

    We are given X¯=25,X¯1=26,X¯2=21

    Let n1+n2=100, where n1 denotes the number of men and n2
    the number of women.

     n2=100n1

    Substituting those values in (i), we have

    25=26n1+21100n1100n1=80 n1+n2=100n2=20

     

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