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प्रश्न
The length of a road roller is 2.1 m and its diameter is 1.4 m. For levelling a ground 500 rotations of the road roller were required. How much area of ground was levelled by the road roller? Find the cost of levelling at the rate of Rs. 7 per sq. m.
उत्तर
Radius of the road roller, r = `1.4/2` = 0.7 m
Length of the road roller, h = 2.1 m
∴ Area levelled by the road roller in one rotation = Curved surface area of the road roller
= 2πrh
= `2 xx 22/7 xx 0.7 xx 2.1`
= 9.24 m2
∴ Area levelled by the road roller in 500 rotations
= 500 × Area levelled by the road roller in one rotation
= 500 × 9.24
= 4620 m2
Rate of levelling the ground = Rs 7/m2
∴ Cost of levelling the ground
= Area of the ground levelled by the road roller × Rate of levelling the ground
= 4620 × 7
= Rs 32,340
Thus, the area of ground levelled by the road roller is 4620 m2 and the cost of levelling the ground is Rs 32,340.
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