Question

You can buy 4 pens for 12 rupees. How many pens can you buy in 72 rupees?
$
  {\text{A}}{\text{. }}64 \\
  {\text{B}}{\text{. }}60 \\
  {\text{C}}{\text{. }}48 \\
  {\text{D}}{\text{. }}24 \\
 $

Answer 1

Hint: Here we go through by the help of a unitary method to solve the question. First we find how many pens we can bring from Rs.1 and then multiply it by 72 to get the answer.

Complete step-by-step answer:
Here in the question it is given that you can buy 4 pens for 12 rupees, we have to find the number of pens at Rs. 72.

For 12 rupees we can buy 4 pens.

In 1 rupees we can buy $\dfrac{4}{{12}}$ pens. (By the help of unitary method)

As we find in Rs.1 we will buy $\dfrac{4}{{12}}$ pens. So for Rs.72 we simply multiply it by 72.

i.e. $\dfrac{4}{{12}} \times 72 = 24$

Hence we can buy 24 pens in 72 rupees.

Note: Whenever we face such a type of question the key concept for solving the question is we have to go through a unitary method and go through what is given in the question. Here in this question the amount is given at the end of the question and we have to find the numbers of pens. So we apply the unitary method on amounts, not on pens. This is the key concept for solving unitary methods.