Arithmetic Aptitude :: Pipes & Cistern
8. One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in 36 min, then the slower alone will be able to fill the tank in:
Lets assume time required by slower pipe alone to fill the tank = x minutes.
Then, faster pipe will fill it in x/3 minutes.
=> 1/x+3/x = 1/36
=>4/x = 1/36 => x = 144 min.