Question

12 bags of wheat weigh 90kg. How much will 20 bags weigh?

Answer 1

Hint: We are given the weight of a certain number of bags and we are required to find the weight of a certain other number of bags. For this we will use the unitary method where we would first try to find out the weight of a single bag and after that multiply that with the number of bags whose weight we want to find out.

Complete step-by-step solution:
Suppose we have ‘n’ quantities and they together weigh ‘k’ units. Then the weight of each unit will be found out by dividing the total weight by the number of units present i.e.:
$\dfrac{k}{n}$
After finding the weight of one unit, we can find the weight of ‘g’ units by multiplying the weight of each unit by ‘g’. Here, we have the information that 12 bags weight 90kg:
$\Rightarrow 12\text{bags}=90kg$
$\Rightarrow 1 \text{bag}=\dfrac{90}{12}kg$
Now, the weight of each bag has been found out. A single bag weighs $\dfrac{15}{2}$kg. Now, we will find the weight of 20 bags:
$20 \text{bags}=\dfrac{90}{12}\times 20$
$\Rightarrow 20 \text{bags}=\dfrac{15}{2}\times 20$
$\Rightarrow 20\text{bags} =150kg$
Hence, if 12 bags weigh 90 kg then 20 bags will weigh 150kg.

Note: If your calculations are fast and accurate you can easily do the division by the number of bags first and then multiply them by the number of bags whose weight is to be found out. But if the calculations are not that accurate, then you must first find the weight per unit and later multiply with the number of bags whose weight is to be found out.