Question

In a school the average score of all 1400 students at an examination was found to be 69.5 The average score of boys in the school was 68 and that of girls was 72 Hence the number of boys and the number of girls respectively are

• A. $680$ and $720$
• B. $720$ and $680$
• C. $875$ and $525$
• D. $800$ and $600$

Answer 1

The correct option is C $875$ and $525$

Let No. of boys = x
No. of girls $=(1400-x)$
$\Rightarrow Average=\frac{x\left(68\right)+(1400-x)72}{1400}$
$\Rightarrow \left(69.5\right)\times 1400=68x+72\times 1400-72x$
No of boys $=x=875$
No of girls $=525$