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A rectangular reservoir is 120m long and 75m wide. At what speed per hourmust water flow into it through a square pipe of 20cm wide so that the waterrises by 2.4m in 18 hours?3 |
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Answer» Length of the reservoir = 120 mBreadth of the reservoir = 75 mThe height of the water level in 18 hours = 2.4 mVolume of the water collected in the reservoir 120× 75× 2.4= 21600 m³Let the speed of the flowing water = x m/hrthe water flowing in the pipe eventually forms a cuboid of width 20 cm or 0.2 m and height of 20 cm or 0.2 m.The length of the cuboid so formed in the pipe in 18 hours = 18x mTherefore, the volume of the water flows out of the pipe in 18 hours = 0.2× 0.2× 18x= 0.72x m³Therefore,Volume of the water collected in the reservoir = volume of the water flows out of the pipe in 18 hours.21600 = 0.72xx = 21600/0.72x = 30000 m/hrOr, speed of the water = 30 km/hr |
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