A rectangular reservoir is `120 ma n d75 mw i d edot` At what speed per hour must water flow into it through a square pipe of `20 c mw i d e` so that the water rises by `2. 4m`in `18hou r sdot`

Explanation

Length of the reservoir = `120 m`
Breadth of the reservoir = `75 m`
The height of the water level in `18 hours = 2.4 m`
Volume of the water collected in the reservoir `=120 xx75 xx 2.4`
`=21600 m^3`
Let the speed of the flowing water =` (xm)/(hr)`
the 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 = 18xxm`
Therefore, the volume of the water flows out of the pipe in` 18 hours = 0.2 xx 0.2 xx 18x`
` 0.72x m^3`
Therefore,Volume of the water collected in the reservoir = volume of the water flows out of the pipe in `18 hours`.
`21600 = 0.72x`