Two pipes A and B can fill a cistern in 37 ½ min and 45 minutes respectively. Both the pipes are opened. The cistern will be filled in just half an hour, if the pipe B is turned off after

a)6 minutes
b)9 minutes
c)45 minutes
d)3 minutes

• If pipe B is turned off after x mins, then
  (2*30)/75 + x/45 =1
  x/45 = 1-60/75 = 1/5
  x= 45/5= 9 mins
  
  so option b) 9 mins
• 12 years agoHelpfull: Yes(3) No(2)