Question

If one orange costs Rs 4.5, how many oranges can be bought for Rs 72?

Answer 1

Hint: This problem is an example of unitary method. In the unitary method, we will find the cost of one unit, then we will find the cost of the required number of units. In our example, we are given the cost of one unit of orange, but instead of the number of units, we are given the final cost of the oranges. Thus, we will alter the basic method a little to find the number of oranges that can be bought for the given amount.

Complete step-by-step solution:
It is given that the cost of one orange is Rs 4.5.
Let us assume that A is the person who has Rs 72 and he intends to buy oranges with his Rs 72.
Through the unitary method, we are able to find the final cost of a thing when we know the cost of one unit and we know how many units are to be bought. It is given as the product of the cost of one unit and the number of units to be bought.
But in our case, we are not given the number of units to be bought, instead, we are given the final cost.
Let us assume that the number of oranges that can be bought with Rs 72 be n.
Therefore, according to the unitary method, the product of the cost of one unit and n must be 72.
$\Rightarrow $ 4.5(n) = 72
Thus, if we divide both sides by 4.5, we can find the value of n.
$\begin{align}
  & \Rightarrow n=\dfrac{72}{4.5} \\
 & \Rightarrow n=16 \\
\end{align}$
Therefore, A can buy 16 oranges with his Rs 72, if each unit costs Rs 4.5.

Note: Unitary method is very basic but is used in many practical problems. One such method could be derived if this question is altered. If each orange cost Rs 4.5 and we have to buy 16 oranges, with the help of the unitary method, we can find the final cost.