Question

The average marks of boys in a 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. $40\%$
• B. $20\%$
• C. $80\%$
• D. $60\%$

Answer 1

The correct option is C $80\%$

Let there are $x$ boys and $y$ girls then

According to the given condition-

$52x+42y=50(x+y)$

$52x+42y=50x+50y$

$2x=8y$

$x=4y.$

Hence, total number of students $=x+y=4y+y=5y.$

% of Boys in the class $=\frac{4y}{5y}\times 100=80$%

$\therefore$ the percentage of boys in the class is $80$%.