Page 146 - Start Up Mathematics_5

7. Ramita sold a washing machine for ` 9,500 at a loss of ` 700. What was the cost price
of the washing machine?

Unitary Method

In unitary method, we first find the value of one unit and then find the value of the required
number of units.
• When 1 thing is given and we need to find for more, we multiply.

• When more is given and we need to find for 1, we divide.
• When more is given and we need to find even more, we first find for 1 by dividing and
then find for more by multiplying. This is called unitary method.

Example 5: The cost of 2 chocolates is ` 65. What is the cost of 8 such chocolates?

Solution: Cost of 2 chocolates = ` 65
Cost of 1 chocolate = ` 65 ÷ 2 = ` 32.50
Cost of 8 chocolates = ` 32.50 × 8 = ` 260.00

Example 6: If a dozen eggs cost ` 36, what is the cost of 22 eggs?

Solution: Cost of 1 dozen eggs = ` 36
i.e., Cost of 12 eggs = ` 36

Cost of 1 egg = ` 36 ÷ 12 = ` 3
Cost of 22 eggs = ` 3 × 22 = ` 66

Example 7: Hariti bought 20 oranges for ` 75. How much will she have to pay if she buys
25 oranges?
Solution: Cost of 20 oranges = ` 75
Cost of 1 orange = ` 75 ÷ 20 = ` 3.75

Cost of 25 oranges = ` 3.75 × 25 = ` 93.75

EXERCISE 10.2

1. Dhruv bought 3 m cloth for ` 270. What is the cost of 7 m cloth?

2. Sonika purchased 15 kg rice for ` 470.25. How much will she pay for 25 kg rice?
3. A train covers 120 km in 1 hour. How much time will it take to cover a distance of
960 km?

4. If the cost of 5 dozen bananas is ` 177.50, what is the cost of 8 dozen bananas?

5. Anirudh purchased 2 scores of balls for ` 2,300. What is the cost of 25 such balls?
(Hint: 1 score = 20)
6. The cost of 5 kg sugar is ` 179. What is the cost of 3 kg sugar?

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