Page 237 - ICSE Math 7

(b) Cost of constructing the road = ` 120 × 411 = ` 49,320
(c) Area of the field including the roads = 80 × 60 = 4,800 m 2
Area of field excluding the roads = 4,800 – 411 = 4,389 m 2

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Cost of levelling the field at the rate of ` 90 per m = 90 × 4,389 = ` 3,95,010

EXERCISE 21.1

1. Find the perimeter and area of the following.
(a) length = 12 cm, breadth = 8 cm (b) length = 20 m, breadth = 15 m

2. Find the area of the square whose: (a) side = 8 cm (b) diagonal = 5.2 cm
3. Find the expenditure of putting a barbed wire around a 4 hectare square field, if it costs
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` 45 per metre. (use 1 hectare = 10,000 m )
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4. The area of a rectangular sheet of aluminium is 400 cm . If the breadth of the sheet is
16 cm, find its length. Also find the perimeter of the aluminium sheet.
5. Calculate the perimeter and area of each of the following figures.

8 cm

10 cm
3 cm 12 cm
(a) (b)
4 cm
7 cm
12 cm
6 cm

2 cm 3 cm
11 cm

6. A playground is 38 m 50 cm long and 61 m 50 cm wide. Find:
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(a) the cost of levelling it at ` 40 per m .
(b) the number of rounds along the boundary one should take to run 2 km.
7. The area of a rectangle is the same as that of a square of side 16 m. If the length of the rectangle
is 32 m, find its perimeter.
8. A picture is painted on a cardboard 8 cm long and 5 cm wide such that there is a margin of
1.5 cm along each of its sides. Find the total area of the margin.

9. A rectangular park has dimension 90 m by 70 m. Two paths run parallel to the lengths of the
rectangle and two paths run parallel to its breadths. The two paths along the length are 7 m wide
and the other two along the breadth are 5 m wide. Find the area of:
(a) all the paths. (b) the remaining portion of the park.

10. The dimensions of a rectangular plot are 35 m by 20 m. A path of uniform width 2 m is built
along the border and inside it. Find the cost of paving the path with bricks at ` 25 per square
metre and also the cost of covering the remaining part of the plot with grass at ` 19 per square
metre.

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