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प्रश्न
A road roller is cylindrical in shape, its circular end has a diameter of 1.4 m and its width is 4 m. It is used to level a play ground measuring 70 m × 40 m. Find the minimum number of complete revolutions that the roller must take in order to cover the entire ground once.
उत्तर
Curved surface area of the road roller = 2πrh
= 2 x `22/7` x 0.7 x 4 = 17.6 cm2
Area of the play ground = 70 x 40 = 2800 m2
∴ Number of revolutions to cover the entire ground = `2800/17.6 = 159 1/11`
∴ Number of complete revolutions = 160.
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