Question

30 bags of wheat of 50 kg, each costs Rs. 2000. Find the cost of 20 bags of wheat weighing 30 kg each.

Answer 1

Hint: This question is simply based on the concept of unitary method. Unitary method is a technique for solving a problem by first finding the value of a single unit, and then finding the necessary value by multiplying the single unit value by the given number of articles/objects/people.

Complete step-by-step solution:
Since this question is based on the unitary method, we know that each bag is 50 kg and here we have a total of 30 bags.
So, weight of 30 bags (50 Kg each)
 \[= 30 \times 50 \\
   = 1500\,Kg \]
Also, according to the question, 1500 Kg of wheat cost Rs. 2000.
So, cost of 1 Kg of wheat is:
\[ \Rightarrow \dfrac{{2000}}{{1500}} = \dfrac{{20}}{{15}}\]
Now the question asks us to calculate the cost of 20 such bags of 30 Kg each.
So, weight of 20 bags (30 Kg each)
\[
   = 20 \times 30 \\
   = 600\]
Therefore, we have to calculate the cost of \[600\,kg\] wheat. We will simply multiply the cost of one kg of wheat with \[600\,\]:
\[ = 600 \times \dfrac{{20}}{{15}}\]
\[ = 800\,\]
So, 20 bags of wheat of 30 Kg will cost \[Rs.\,800\].

Note: This was a simple question based on the unitary method. This unitary method has many practical applications; they are used in problems of speed, distance, time to the problems related to calculating the cost of materials.