IBPS Clerk Prelims Model Paper 8

Question : 56 of 100

Marks: +1, -0

Six pipes are fitted to a water tank. Some of these pipes are used for filling, while others are used for emptying. Each filling pipe can fill the tank in eighteen hours and each emptying pipe can empty the tank in twelve hours. On opening all the pipes, an empty tank can be filled in eighteen hours. The number of emptying pipes is