Question

Pipe a can fill a tank in 36 minutes. pipe b can fill the same tank in 72 minutes. there is a drain pipe, pipe c, at the bottom of the tank. a man opens pipe a and pipe b when the tank is empty and returns back to shut them when the tank should overflow. however, he finds that he had kept pipe c also open and shuts it immediately. the tank overflows in the next 6 minutes. how long will pipe c take to drain the tank, if pipes a and b are kept shut?

Answer 1

Time taken to fill a tank by pipe A = 36min

Time taken to fill a tank by pipe B = 72 min

Time taken to fill a tank by pipe C = 72+36 = 108min