Question

Mr. Colin bought $800$ books. He sold $65\%$ of them at $Rs15$ each, $60\%$ of the remainder at a discount of $40\%$ and the rest of the books at cost price. If he earned $Rs1056$, find the cost price of each book.

• A. $Rs10$
• B. $Rs18$
• C. $Rs12$
• D. $Rs16$

Answer 1

The correct option is C $Rs12$

Mr. Colin bought 800 books. He sold $65\%$ of them at $Rs15$ each.

.Number of books sold at $Rs.15$ $=\frac{65}{100}\times 800$

$=520$

Let the cost price of the book be $Rs.x$

Profit on these $520$ books $=520(15-x)$

Thus,

Remaining book $=(800-520)$

$=280$

60% of the remainder at a discount of $40\%$.

Number of books at $40\%$ discount $=280\times \frac{60}{100}$

$=168$

Loss on these 168 books $=168(x-15\times \frac{60}{100})$

$=168(x-9)$

Total earning $=1056$

$=>520(15-x)-168\times (x-9)=1056$

$=>7800-520x-168x+1512=1056$

$=>688x=8256$

$=>x=12$

Thus, the cost price of the book is $Rs.12$