# Mixing problem involving 3 inlets and 2 outlet pipes

1. Aug 6, 2006

### tin llenaresas

help!
how do we solve a mixing problem involving 3 inlet pipes and 2 outlet pipes?is it okay to just add up the 3 rates of input as well as their respective concentrations?
all the sample problems i have encountered involves only 1 inlet and one outlet pipe..

2. Aug 6, 2006

### HallsofIvy

Staff Emeritus
You start by actually explaining the problem! You could have could have one pipe that goes back to the tank itself with two additional inlet pipes and one additional outlet or any variation on that.

Do you have a single tank with 3 pipes coming in and two pipes going out? If that is the case, then, yes, you can treat that as a single with the sum of the inputs. But be careful about how you sum that- you can't just add the concentrations. You have to sum the amount of "substance" that comes in every second. For example, if you have one pipe bringing in a solution at 3 L/s, with concentration 10 g/L of salt and a second pipe bringing in a solution at 5 L/s with concentration 5 g/L of salt, then the first pipe will bring in (3 L/m)(10 g/L)= 30 g/s and the second will bring in (5 L/s)(5 g/L)= 25 g/s. The two pipes will bring in a total of 30+25= 55 g/s. That's the information you need to set up your equation.

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