Question

If the cost of $7\,kg$ of rice is $Rs.\,168$ , what is the cost of $105\,kg$ of rice?
A. $Rs.\,2,580$
B. $Rs.\,2,630$
C. $Rs.\,2,520$
D. $Rs.\,2,500$

Answer 1

Hint: Here it is given the cost of some kilogram of rice and we have to find the cost of another kilogram of rice given. We will use the unitary method in this question so the first step will be to calculate the cost of one kilogram of rice. Then we will multiply the cost we got by the kilogram of rice whose cost is to be determined. Finally we will solve the value and get the desired answer.

Complete step by step answer:
It is given to us that the cost of $7\,kg$ rice is $Rs.\,168$ so we can write this as follows:
Cost of $7\,kg$ Rice $=Rs.\,168$
Now we will use Unitary Method for finding the cost of $1\,kg$ of rice.
So we will divide both sides by $7$ for calculating cost of $1\,kg$ rice as follows:
Cost of $\dfrac{7\,kg}{7}$ Rice $=\dfrac{Rs.\,168}{7}$
Cost of $1\,kg=Rs.\,24$……$\left( 1 \right)$
So we got that cost of $1\,kg$ rice is $Rs.\,24$ from equation (1).Next we have to find the cost of $105\,kg$ rice so we will multiply equation (1) by $105$ on both sides as follows:
Cost of $105\,kg=Rs.\,24\times 105$
Cost of $105\,kg=Rs.\,2520$

Hence cost of $105\,kg$ rice is $Rs.\,2520$.

Note: We have used the unitary method in this question which is a technique where we try to find the value of each unit of the given quantity. In this method first we find the value of a single unit and then multiply it with the amount of quantity whose value is to be determined. By finding the cost of one unit it becomes easy to calculate the cost of any unit given and also the equation doesn't get complicated.