A water tank has 8 pipes in total. Some are filling pipes and the rest are drainage pipes. Each filling pipe can fill 1/12 of the tank per hour, while...
Question
A water tank has 8 pipes in total. Some are filling pipes and the rest are drainage pipes. Each filling pipe can fill 1/12 of the tank per hour, while each drainage pipe can empty 1/36 of the tank per hour. When all pipes are opened simultaneously, an empty tank gets filled in 3 hours. How many drainage pipes are there?