Question

A hole can empty a full tank in 60 minutes. To maintain the level of water in
the tank, 3 filling pipes of equal efficiency are required. How many more such
pipes are required if we want tank to be filled in 180 minutes?

Answer 1

Answer:

Assume the work to be done is 180 units. So the efficiency of the hole is -180/60= -3 units/ min. Now to maintain the level filling pipes are required that three feeling spikes pipes

offset the negative work done by the hole. Thus, efficiency of each filling pipe is +1 unit/min. Now.. we want an empty tank to be filled in 180 minutes. This means that the efficiency of the whole

system should be 180/180= 1 unit/min. With 3 pipes, we already offset the negative work done by the whole.

To make the efficiency 1 unit/min, we would need 1 more filling pipe. Thus, the answer is 1...

so the answer is 1