RD Sharma Class 6 Solutions Chapter 9 - Ratio, Proportion and Unitary Method (Ex 9.4) Exercise 9.4

Unitary Method is used in our day to day life as well such as

• To find how much petrol will our car need for 20 km, it runs at 12 km per liter.

• To find how much would 200 pens cost if 50 pens cost 20 rupees.

• To find out much time it would take a person to go to school if he drives at 40 km/hr, and it takes 1 hour to reach him if he drives at 20 km/hr.

• To find out the number of labor required to build up a house in a specific period.

To determine values about a single unit, Unitary Method is used. Unitary-method can be used to calculate measurements, etc. The unitary method is used to solve problems if there is variation in the given quantity. In this method, the value of one single unit is calculated first and then the value of the required quantities which can be obtained by arithmetic operations. The formula used to calculate the unitary method is

Value of one unit = [\frac{ \text {Total Value}}{\text{No. of Units}}]

Given:

 Cost of 5 notebooks= 200

 Cost of 1 notebook= [\frac{200}{5}]=40

• The number of notebooks that can be purchased with 40 Rupees= 1

The number of notebooks that can be purchased with 1 Rupee= 1/40

Therefore, the number of notebooks that can be purchased with 400 rupees= 1/40 x 400 =10

• The cost of 1 notebook= 40 Rupees

The cost of 20 notebooks= 40 x 20= 800 Rupees