CLASS-8UNITARY METHOD-MULTIPLYING RATIO

MULTIPLYING RATIO

We can say that, problems related to both direct & inverse variation can be solved by finding what is known as the multiplying ratio.

For your better understanding we would like to give some example –

Example.1) If 8 kg of rice costs \$ 320, find the cost of 15 kg of rice

Answer) Since the cost increases when the weight increases, this an example of Direct variation

So, the ratio of the weight = the ratio of the corresponding costs

8         \$ 320

So, ------- = ---------, where \$ x is the cost of 15 kg of rice

15           x

\$ 320 X 15

So,  x  = -------------- =  \$ 600

8

15

Here  --------- is the multiplying ratio.

8

If, two quantity changes in the same ratio, the multiplying ratio is the inverse of the ratio.

Another way –

As per the given condition, 8 kg of rice costs \$ 320

\$ 320

Then, 1 kg of rice costs = ----------

8

[ here we divide total price (\$ 320) by quantity (8 kg), because the cost of 1 kg rice will be less than 8 kg rice ]

15

Now, the cost of 15 kg rice will be = \$ 320 X ---------

8

(here 15 / 8 is the multiplying ratio)

[ here we will multiply by the given quantity which is 15 kg with the cost of 1 kg rice ]

=  \$ 600     (Ans.)