If two pipes function simultaneously, the reservoir will be filled in 6 hours. One pipe fills the reservoir 5 hours faster than the other. How many hours does it take the second pipe to fill the reservoir ?
Solution: Let the reservoir be filled by first pipe in x hours.
Then, second pipe will fill it in (x+5) hours.
.'. 1/x + 1/(x+5) = 1/6
=> (x+5+x)/(x(x+5)) = 1/6.
x^2 - 7x - 30 = 0
=> (x - 10)(x +3) = 0
x = 10
So, the second pipe will take (x+5) = 10+5 = 15 hours to fill the reservoir.
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