Q:

A tank can be filled with water by two pipes A and B together in 36 minutes. If the pipe B was closed after 30 minutes, the tank is filled in 40 minutes. The pipe B can alone fill the tank in?

• 1
  45 minutes
• 2
  60 minutes
• 3
  75 minutes
• 4
  90 minutes
• 5
  85 minutes