A cistern (Latin meaning- “Box” & Greek meaning – “basket”) is a waterproof receptacle for holding liquids, usually water.
While dealing with this topic, we have to focus on two kinds of pipes:
Filling pipes or inlet pipes
Emptying pipes or outlet pipes (can also be mentioned as “Leaks” and “Cracks”, as in each case water is coming out of cistern)
The general method to solve a Pipes and Cisterns problem is by using fraction method which is quite common. But by this method, there are high chances of calculation mistakes. Sometimes, the solution might become lengthy while dealing with large numbers. A better method to deal with such questions is called LCM Method
In LCM Method, we deal with efficiencies of pipes. As we know that inlet pipes will fill the tank, so their efficiencies will always be Positive. On the other-hand, Outlet pipes or leaks will lead to removal of liquid from the tank, so their efficiencies will always be Negative.
Efficiency of any pipe = Liters of liquid the pipe can fill or remove per unit time.
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