Question

Fifteen postcards cost $Rs.2.25$. What will be the cost of $36$ postcards? How many postcards can we buy in $Rs.45$

Answer 1

By using unitary method, we can find the value of $1$ item, dividing the total cost of many items by number of items.

In the similar way, we can find the cost of many items when we have the cost of one item by using unitary method.

$15$ postcards costs $=Rs.2.25$

$1$ postcard will cost $=Rs.\frac{2.25}{15}=Rs0.15$

$36$ postcards will cost $=Rs.0.15\times 36=Rs5.40$

And,

In $Rs.2.25$ we can buy $=15$ postcards

In $Rs.1$ we can buy $=\frac{15}{2.25}$ postcards

In $Rs.45$ we can buy $=\frac{15}{2.25}\times 45$ postcards

$=300$ postcards