Question

If half a litre of milk costs 22 rupees, how much will 7 litres cost?

Answer 1

Hint: Here in this question we use the concept of unitary method which helps us in finding the value of large quantities if we are given value for a single quantity and vice versa.
* If we have \[x\] as the value of one item and we have to find value of \[m\] number of items, we simply multiply value of single item with number of items i.e. \[ = x \times m\]
* If we have \[x\] as the value of \[m\] number of items, then to find the value of one item we simply divide the total value of \[m\] items by number of items i.e. \[ = \dfrac{x}{m}\]
* A litre consists of two half litres.

Complete step-by-step solution:

Given, the price of half litres of milk is rupees 22.

To find the price of one litre of milk, multiply 22 by 2. The price of one litre of milk is rupees 44.
Find the price of 7 litres of milk by multiplying the price of 1 litre of milk by 7, that is \[44 \times 7 = 308\].

Therefore, the price of 7 litres of milk is rupees 308.

Note: Unitary method is used in these types of problems, even in our day to day life.
Common mistake done while dividing or multiplying in unitary method is when all the values are not in same S.I unit, i.e. for example if \[x\] is in \[cm\] and \[y\] is in \[m\], then when dividing or multiplying both the values we will not get right answer, so we should either convert \[cm\] into \[m\] or vice versa.