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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20.png)
(2) Find the area of a rectangular plot, one side of which is 48 m and its diagonal is 50 m.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-1.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-2.png)
(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?
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-3.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-4.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-5.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-6.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-7.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-8.png)
(10) Find the area of square each of whose sides 8.5 m.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-9.png)
(11) Find the area of the square, the length of its diagonal.
(i) 72 cm, (ii) 2.4 m.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-10.png)
(12) The area of a square is 16200 m2. Find the length of its diagonal.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-11.png)
(13) The area of a square field is ½ hectare. Find the length of its diagonal in metres.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-12.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-13.png)
(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?
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-14.png)
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-15.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-16.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-17.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-18.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-19.png)
(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.
![](https://www.netexplanations.com/wp-content/uploads/2018/10/Mensuration-Class-7-EX-20-20.png)
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