RS Aggarwal Class 7 Mathematics Twentieth Chapter Mensuration Exercise 20B Solution
EXERCISE 20B
(1) A rectangular grassy plot is 75 m long and 60 m broad. It has a path of width 2 m all around it on the inside. Find the area of the path and the cost of constructing it at Rs 125 per m2.
(2) A rectangular plot of land measures 95 m by 72 m. Inside the plot, a path of uniform width of 3.5 m is to be constructed all around. The rest of the plot is to be laid with grass. Find the total expenses involved in constructing the path at Rs 80 per m2 and lying the grass at Rs 40 per m2.
(3) A saree is 5 m long and 1.3 m wide. A border of width 25 cm is printed along its sides. Find the cost of printing the border at Rs 1 per 10 cm2.
(4) A rectangular grassy lawn measuring 38 m by 25 m has been surround externally by a 2.5 m wide path. Calculate the cost of gravelling the path at the rate of Rs 120 per m2.
(5) A room 9.5 m long and 6 m wide is surrounded by a 1.25 m wide verandah. Calculate the cost of cementing the floor of this verandah at Rs 80 per m2.
(6) Each side of a square flower bed is 2 m 80 cm long. It is extended by digging a strip 30 cm wide all around it. Find the area of the enlarged flower bed and also the increase in the area of the flower bed.
(7) The length and breadth of a park are in the ratio 2 : 1 and its perimeter is 240 m. A path 2 m wide runs inside it, along its boundary. Find the cost of paving the path at Rs 80 per m2.
(8) A school has a hall which is 22 m long and 15.5 m broad. A carpet is laid inside the hall leaving all around a margin of 75 cm from the walls. Find the area of the carpet and the area of the strip left uncovered. If the width of the carpet is 82 cm, find its cost at the rate of Rs 60 per m.
(9) A square lawn is surrounded by a path 2.5 m wide. If the area of the path is 165 m2, find the area of the lawn.
(10) The length and breadth of a rectangular park are in the ratio 5 : 2. A 2.5 m wide path running all around the outside of the park has an area of 305 m2. Find the dimensions of the park.
(11) A rectangular lawn 70 m by 50 m has two roads, each 5 m wide, running through its middle, one parallel to its length and the other parallel to its breadth. Find the cost of gravelling the roads at Rs 60 per m2.
(12) A 115 m long and 64 m broad lawn has two roads at right angles, one 2 m wide, running parallel to its length, and the other 2.5 m wide, running parallel to its breadth. Find the cost of gravelling the roads at Rs 60 per m2.
(13) A rectangular field is 50 m by 40 m. It has two roads through its center, running parallel to its sides. The width of the longer and the shorter roads are 2 m and 2.5 m respectively. Find the area of the roads and the area of the remaining portion of the field.
(14) Calculate the area of the shaded region in each of the figures given below:
(15) Calculate the area of the shaded region in each of the figures given below.
Fig (ii) has a uniform width of 3 cm and it is given that AB = CD.
(16) In the given figure, all steps are 0.5 m high. Find the area of the shaded region.
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