Page 92 - Start Up Mathematics_4

Example 20: A man earns ` 12,000 in 10 days. How much will he earn in 18 days?

Solution: Earning in 10 days = ` 12,000

Earning in 1 day = ` 12,000 ÷ 10 = ` 1,200
Earning in 18 days = ` 1,200 × 18 = ` 21,600
So, the man earns ` 21,600 in 18 days.

EXERCISE 6.7

1. In 5 days, Rahul eats 20 chocolates. How many chocolates can he eat in 16 days?
2. A tailor needs 18 m of cloth to stitch 9 shirts of the same size. How much cloth will
he need to stitch 15 shirts?

3. The cost of 4 L milk is ` 120. What is the cost of 6 L milk?

4. A factory makes 7,000 toy cars in 25 days. How many toy cars will be made in 50 days?
5. Sohail earns ` 9,060 in 15 days. How much will he earn in the month of March?

6. Mr Jha bought 150 pairs of socks for ` 3,000. Remember
What will be the cost of 250 pairs?
We follow the order (DMAS) to
simplify a problem.
D → Division
M → Multiplication
Mixed Problems A → Addition

Example 21: Simplify 128 ÷ 16 × 5 + 320 × 4 – 150 + 280. S → Subtraction
Solution: 128 ÷ 16 × 5 + 320 × 4 – 150 + 280 (Divide: 128 ÷ 16 = 8)

= 8 × 5 + 320 × 4 – 150 + 280 (Multiply: 8 × 5 = 40, 320 × 4 = 1,280)
= 40 + 1,280 – 150 + 280 (Put numbers with the same signs
together)

= 40 + 1,280 + 280 – 150 (Add: 40 + 1,280 + 280 = 1,600)
= 1,600 – 150 (Subtract)
= 1,450

Example 22: For the school sports day, ` 30,000 was collected from 200 150
students. How much money did each student give? If there 2 300
are 350 students in the school, how much money is yet to be – 2
collected? 10
Solution: Money collected = ` 30,000 – 10

Number of students = 200 00
Money given by each student = ` 30,000 ÷ 200 = ` 150 – 0
Total number of students = 350 0

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