Two pipes P and Q together can fill a tank in 15 hours.If P alone takes 1/2 of the time of thrice Q's then the time taken by Q alone to fill the tank is:
Assume Q alone takes U hours to fill the tank.
Then P takes = 1/2 of 3U = 3U/2 hours.
Now, Q's 1 hours work = 1/U and P's 1 hours work = 2/3U.
Given that, (P+Q) takes = 15 hours.
Then (P+Q)'s 1 hour's work = 1/15. So 1/15 = 1/U + 2/3U.
5/3U = 1/15
U = 25
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