RS Aggarwal Class 7 Mathematics Twentieth Chapter Mensuration Exercise 20A Solution
EXERCISE 20A
(1) Find the area of the rectangle whose dimensions are:
(i) Length = 24.5 m, breadth = 18 m
(ii) Length = 12.5 m, Breadth = 8 dm.
(2) Find the area of a rectangular plot, one side of which is 48 m and its diagonal is 50 m.
(3) The sides of a rectangular park are in the ratio 4 : 3. If its area is 1728 m2, find the cost of fencing it at Rs 30 per metre.
(4) The area of a rectangular field is 3584 m2 and its length is 64 m. A boy runs around the field at the rate of 6 km/h. How long will he take to go 5 times around it?
(5) A verandah is 40 m long and 15 m broad. It is to be paved with stones, each measuring 6 dm by 5 dm. Find the number of stones required.
(6) Find the cost of carpeting a room 13 m by 9 m with a carpet of width 75 cm at the rate of Rs 105 per metre.
(7) The cost of carpeting a room 15 m long with a carpet of width 75 cm at Rs 80 per metre is Rs 19200. Find the width of the room.
(8) The length and breadth of a rectangular piece of land are in the ratio of 5 : 3. If the total cost of fencing it at Rs 24 per metre is Rs 9600, find its length and breadth.
(9) Find the length of the largest pole that can be placed in a hall 10 m long, 10 m wide and 5 m high.
(10) Find the area of square each of whose sides 8.5 m.
(11) Find the area of the square, the length of its diagonal.
(i) 72 cm, (ii) 2.4 m.
(12) The area of a square is 16200 m2. Find the length of its diagonal.
(13) The area of a square field is ½ hectare. Find the length of its diagonal in metres.
(14) The area of a square plot is 6084 m2. Find the length of the wire which can go four times along the boundary of the plot.
(15) A wire is in the shape of a square of side 10 cm. If the wire is rebent into a rectangle of length 12 cm, find its breadth. Which figure encloses more area and by how much?
(16) A godown is 50 m long, 40 m broad and 10 m high. Find the cost of whitewashing its four walls and ceiling at Rs 20 per square metre.
(17) The area of the 4 walls of a room is 168 m2. The breadth and height of the room are 10 m and 4 m respectively. Find the length of the room.
(18) The area of the 4 walls of a room is 77 m2. The length and breadth of the room are 7.5 m and 3.5 m respectively. Find the height of the room.
(19) The area of four walls of a room is 120 m2. If the length of the room is twice its breadth and the height is 4 m, find the area of the floor.
(20) A room is 8.5 m long, 6.5 m broad and 3.4 m high. It has two doors, each measuring (1.5 m by 1 m) and two windows, each measuring (2 m by 1 m). Find the cost of planting its four walls at Rs 160 per m2.
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