Question

You want to sell a books for Rs. $96$ and gains as much percent as the cost price of the book. Find the gain $\%$ of the book.

• A. $12$
• B. $24$1
• C. $36$
• D. $48$

Answer 1

Answer: (C)

$36$

Let the C.P. of the book be $x$
Gain $\%=x\%$ of $x=$ $\frac{x^2}{100}$
S.P. $=$ C.P. $+$ gain
S.P. $=96$
Therefore, $x+\frac{x^2}{100}=96$
$100x+x^2=9600$
$x^2+100x-9600=0$
$(x+160)(x-60)=0$
$x=-160$ or $60$
Price cannot be negative.
Gain $\%=x\%$ of $x$
$=$ $\frac{60}{100}\times 60$
$=36$