SOLUTION: A water tank has two drainpipes attached to it. The larger pipe can drain the tank in 2 hours less than the smaller pipe. If both pipes are being used, they can drain the tank in 4

Question 435759: A water tank has two drainpipes attached to it. The larger pipe can drain the tank in 2 hours less than the smaller pipe. If both pipes are being used, they can drain the tank in 4 hours. How long would it takw the smaller pipe to drain the tank working alone?
Answer by jorel1380(3719) (Show Source): You can put this solution on YOUR website!
1/t+1/t-2=1/4
4(t-2)+4t=t(t-2)
4t-8+4t=t2-2t
t2-10t+8=0

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=68 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 9.12310562561766, 0.876894374382339. Here's your graph:

Ignoring the 0 answer, we get t=9.12311
hours and t-2 to be 7.12311 hours..

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