One pipe can fill a tank four times as fast as another pipe. If together the two pipes can fill the tank in 28 minutes, then the slower pipe alone will be able to fill the tank in:
A)35 min B)70 min C)90 min D)140 min

• let 1st pipe can fill the tank in = x min
  and 2nd pipe can fill the tank in = x/4 min
  so both of them can fill the tank in = (1/x)+(4/x) = 1/28
  therefore x = 140 min
• 3 years agoHelpfull: Yes(0) No(2)