Question

The average of marks obtained by $120$ candidates was $35$. If average of the passed candidates was $39$ and that of the failed candidates was $15$, then the number of those candidates, who passed the examination, was

• A. $120$
• B. $110$
• C. $100$
• D. $150$

Answer 1

Answer: (C)

$100$

It is given that the total number of candidates is $120$.

Let the number of passed candidates be $x$.

Then the number of failed candidates will be $120-x$.

Since it is given that the average of the passed candidates is $39$ and average of the failed candidates is $15$, therefore we have:

$[x\times 39+(120-x)\times 15]=120\times 35$
$\Rightarrow 39x+1800-15x=4200$
$\Rightarrow 24x=4200-1800$
$\Rightarrow 24x=2400$
$\Rightarrow x=\frac{2400}{24}$
$\Rightarrow x=100$

Hence, $100$ candidates passed the examination.