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1. 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 ?
- A. 4
- B. 4
- C. 4
- D. 4
Answer: Option C
Explanation:
(A + B) ' 2 hours work when open d = 1/6 + 1/4 = 5/12
(A + B) 4 hours work when open = 5/12 × 2 = 5/6
Remaining work 1 - 5/6 = 1/6
Now, its A turn in 5th hour
1/6 work will be done by A in 1 hour
Total time = 4 + 1 = 5 hours
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