Question

A book seller bought 200 textbooks for Rs.12000. He wanted to sell them at a profit so that he could get 24 books for free. At what profit percent should he sell them?
$
  {\text{A}}{\text{. 10}} \\
  {\text{B}}{\text{. 11}} \\
  {\text{C}}{\text{. 12}} \\
  {\text{D}}{\text{. 13}} \\
 $

Answer 1

Hint: - Here we go through by calculating the cost price of one book and after that we will be able to calculate the profit by multiplying the cost price of one book to the no of books he gets free. Then by applying formula we will simply calculate the profit percent.

Complete step-by-step answer:
Here in the question it is given that the cost price (C.P) of 200 textbooks is Rs.12000.
And now by applying unitary method we will find the cost price of one book i.e.
C.P. of 1 textbook$ = Rs.\dfrac{{12000}}{{200}} = Rs.60$
And in the question it is also given that he gets 24 books free, that is his profit.
So we can calculate the total profit by multiplying the cost price of one book with the 24 books.
I.e. Profit = C.P. of 24 textbooks=$Rs.60 \times 24 = 1440$
And now we will calculate the selling price (S.P) by adding the profit to the cost price of the books.
$\therefore $ S.P. of 200 textbooks = C.P. of 200 textbooks + C.P. of 24 textbooks = C.P. of 224 textbooks
∴ S.P. of 224 textbooks=$224 \times 60 = Rs.13440$
And we know that the formula of profit percent i.e. Profit%$ = \dfrac{{\left( {S.P - C.P} \right)}}{{C.P}} \times 100$
Now we put the values in the formula we get,
Profit%$ = \dfrac{{\left( {13440 - 12000} \right)}}{{12000}} \times 100 = \dfrac{{1440}}{{12000}} \times 100 = 12\% $
Hence option C is the correct answer.

Note: Whenever we face such a type of question the key concept for solving the question is to first have to calculate the profit that he earns then add the profit to the cost price of the objects to find out the selling price. And when we know the value of cost price and selling price we will easily find out the profit percent.