The average marks of boys in class is 52 and that of girls is 42. The average marks of boys and girls combined is 50. The percentage of boys in the class is
A.
80
B.
60
C.
40
D.
20
Answer :
80
Solution :
Let the number of boys be $$x$$ and that of girls be $$y.$$
$$\eqalign{
& \Rightarrow \,\,52x + 42y = 50\left( {x + y} \right) \cr
& \Rightarrow \,\,52x - 50x = 50y - 42y \cr
& \Rightarrow \,\,2x = 8y \cr
& \Rightarrow \,\,\frac{x}{y} = \frac{4}{1}\,{\text{and }}\frac{x}{{x + y}} = \frac{4}{5} \cr} $$
Required % of boys $$ = \frac{x}{{x + y}} \times 100 = \frac{4}{5} \times 100 = 80\% $$
Releted MCQ Question on Statistics and Probability >> Statistics
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