Question

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 1

The correct option is A

80

Let the number of boys be $x$ and that of girls be $y$.
$\Rightarrow 52x+42y=50(x+y)$

$\Rightarrow 52x-50x=50y-42y$

$\Rightarrow 2x=8y\Rightarrow \frac{x}{y}=\frac{4}{1}$ and $\frac{x}{x+y}=\frac{4}{5}$
Required % of boys $=\frac{x}{x+y}\times 100=\frac{4}{5}\times 100=80\%$