Two pipes A and B can fill a tank in 6 hours and 4 hours respectively. If they are opened on alternate hours and if pipe A is opened first, in how many hours, the tank shall be full ?
Answer: B
(A+B)'s 2 hour's work when opened =
Now, its A turn in 5th hour
1/6 work will be done by A in 1 hour
Total time = 4 + 1 = 5 hours