Two pipes A and B can fill an empty tank in 8 hours and 12 hours respectively. They are opened alternately for 1 hour each, starting with pipe A first. In how many hours will the empty tank be filled?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. (19/2)
| Concept | Application |
| Pipe and cistern |
A's 1-hour work = 1/8 B's 1-hour work = 1/12 After 2- hours workdone (A's + B's) = 1/8 + 1/12 = 5/24 After 8 - hours workdone = 20/24 = 5/6 After 9- hours workdone = 5/6 + 1/8 = 23/24 remaining work = 1 - 23/24 = 1/24, will be done by B in 1/2 hours. So total time = 9 + 1/2 = 19/2 hours |