A group of fire brigade personnel carried a right circular cylindrical tank filled with water and pumped out water at a speed of 420 metres per minute to put the fire in 40 minutes by three pipes of 2 cm diameter each. If the diameter of the tank is `2* 8` metres and its length is 6 metre, then calculate (a) what volume of water has been spent in putting out the fire and (b) hte volume of water that still remains in the tank .

Explanation

`2cm=(2)/(100) ` metre `= 0.02` metre.
The volume of water pumped out in 40 minutes by one pipe
`= (22)/(7) xx ((0.02)/(2))^(2)xx 420xx40` cubic.metres` = (22xx0.01xx0.01xx420xx40)/(7)` cubic-metres
`= 22 xx 0.01 xx 0.01 xx 60 xx 40` cubic. metres .
`:.` The volume of water pumped out in 40 minutes by three pipes
` = 3 xx 22xx0.01xx0.01xx60xx40` cubic.metres.
`= 3 xx 22 xx 0.01xx0.01 xx 60 xx 40 xx 1000` cubic. dcm `= 15840` cubic.dcm `= 15840` litres
The volume of the tank `= (22)/(7) xx ((2.8)/(2))^(2)xx6` cubic. metres
`= (22 xx 1.4xx1.4xx6)/(7) ` cubic. metres `= 36960` cubic. dcm `= 36960` litres
`:.` the water still remains `= (36960-15840)` litres `= 21120` litres.