Page 235 - Start Up Mathematics_6

Example 21: Cost of 3 dozen oranges is ` 90. How many oranges can be purchased for ` 17.50?

Solution: Oranges one can buy with 90 rupees = 36 ( 3 dozen = 12 × 3)
36
Oranges one can buy with ` 1 =
90
36
Oranges one can by with ` 17.50 = × 17.50 = 7
90
Example 22: Gaurav purchases 10 books for ` 160 and Karan buys 7 books for ` 105. Who got
the books cheaper?
Solution: Cost of 10 books purchased by Gaurav = ` 160

Cost of 1 book purchased by Gaurav = 160 ÷ 10 = ` 16
Cost of 7 books purchased by Karan = ` 105

Cost of 1 book purchased by Karan = 105 ÷ 7 = ` 15
Clearly, Karan got the books cheaper.

Example 23: Ramesh earns ` 36,800 in 16 months.
(a) How much does he earn in 5 months?
(b) In how many months will he earn ` 55,200?
Solution: (a) Ramesh’s 16 months earning = ` 36,800
,
` 36 800
Ramesh’s 1 month earning = = ` 2,300
16
Ramesh’s 5 months earning = 2,300 × 5 = ` 11,500
(b) Since, the number of months is to be found, therefore it will come on RHS.

` 36,800 can be earned in = 16 months
16
` 1 can be earned in = months
36 ,800
16
` 55,200 can be earned in = × 55,200
36 ,800
= 24 months

EXERCISE 12.3

1. The cost of 10 kg rice is ` 245. Find the cost of 3 kg rice.

2. The cost of 35 inland letters is ` 105. What will be the cost of 60 such inland letters?
3. The weight of 12 tables is 132 kg. What will be the weight of 5 such tables?

4. In Himachal Pradesh, the rainfall was 366 mm in the last four days. If the weather conditions
and rainfall remain the same, how much rainfall is expected in a week?
5. The cost of a dozen eggs is ` 30. What will the cost of 15 eggs?

6. Himanshu purchased 7 pens for ` 91 and Shubham bought 9 pens of the same quality for
` 108. Who bought the pens at a cheaper rate?

7. If 16 L petrol is required to cover a distance of 256 km, then how much petrol is required
to cover a distance of 400 km?

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