How many pencils can we purchase with 20 rupees if one pencil costs 2 rupees?

Hint: We will use the unitary method to find the number of pencils we can purchase from 20 rupees. We will divide the total cost of pencils with the cost of one pencil to get the total number of pencils.

Complete step by step answer:
It is given in the question that the cost of 1 pencil is 2 rupees and the total money in hand is rupees 20. Then, we have to find the total number of pencils we can purchase with rupees 20. Here, to find the total number of pencils we will use the unitary method.

Basically, the unitary method is a mathematical approach to find the value of a single unit and then multiply or divide according to the requirement we have to get the desired result.
For example, the cost of 2 mangoes is rupees 10 then, the cost of one mango will be $\dfrac{10}{2}=5$rupees. Now, we can find the cost of ‘$n$’ mangoes as $(5\times n)$. Similarly, we have total cost to spend as rupees 20, and the cost of 1 pencil is rupees 2. So, the number of pencils that we can purchase in rupees 20 is given by – total amount of money ÷ cost of 1 pencil.
$=\dfrac{Rs.20}{Rs.2}$
$=10$ Pencils.
Therefore, we can purchase 10 pencils in rupees 20.

Note: When every type of question arises it is preferred to find the value of ‘$n$’ unit because, if we know the value of 1 unit then we can directly find the ‘$n$’ unit. So, always try to find the value of 1 unit in this type of question and apply a unitary method.