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

$\overline{X}=\frac{{n}_{1}{\overline{X}}_{1}+{n}_{2}{\overline{X}}_{2}}{{n}_{1}+{n}_{2}}$

We are given $\overline{X}=25,{\overline{X}}_{1}=26,{\overline{X}}_{2}=21$

Let  denotes the number of men and ${n}_{2}$
the number of women.

Substituting those values in (i), we have

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