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  4. In a group of students, mean weight of boys is 80 kg and mean weight of girls is 50 kg. If the mean weight of all the students taken together is 60 kg, then the ratio of the number of boys so that of girls is

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Q. In a group of students, mean weight of boys is 80 kg and mean weight of girls is 50 kg. If the mean weight of all the students taken together is 60 kg, then the ratio of the number of boys so that of girls is

Statistics

Solution:

Let the number of boys be $n_1$ and that of girls be $n_2$, then
$60 = \frac{80n_{1} + 50n_{2}}{n_{1}+n_{2}} $
$\Rightarrow 60n_{1} + 60n_{2} = 80n_{1}+50n_{2}$
$ \Rightarrow 10n_{2}= 20n_{1} \Rightarrow n_{1} : n_{2} : : 1 :2$