6th Maths : Term 1 Unit 3

Ratio and Proportion

Unitary Method

Finding the value of one unit and then using it to find the value of the required number of units is known as unitary method.

Express the given problem in Mathematical statement.

Find the value of one unit of the given item using division.

Find the value of the required number of the same items using multiplication.

Pari wants to buy 5 tennis balls from a sports shop. If a dozen balls cost ₹ 180, how much should Pari pay to buy 5 balls?

Solution

By unitary method, we can solve this as follows:

Cost of a dozen balls = ₹ 180

\(\Rightarrow\) Cost of 12 balls = ₹ 180

Cost of 1 ball = \(\frac{180}{12}\) = ₹ 15

Cost of 5 balls = \(5 \times 15\) = ₹ 75

Hence, Pari has to pay ₹ 75 for 5 balls.

A heater uses 3 units of electricity in 40 minutes. How many units does it consume in 2 hours?

Solution

In 40 minutes, electricity used = 3 units.

In 1 minute, electricity used = \(\frac{3}{40}\) units.

In 120 minutes (2 hours), electricity used = \(\frac{3}{40} \times 120 = 9\) units

Thus, the heater consumed 9 units of electricity in 2 hours.