- #1

tickle_monste

- 69

- 1

And that's it, that's all my book explains. It doesn't explain at all what to do when you're both changing the water level and adding more brine to the tank. The author doesn't even

*hint*at a method for solving it:

Adding brine, but not changing the water level:

Adding brine, but not changing the water level:

100 gallon tank, 3 gals/min brine flow in at 2 lbs of salt per gallon, 3 gals/min of the mix flow out.

dx = 6dt (brine) - (x/100)3dt.

dx/(x-200) = -.03dt.

Separable, hooray.

Not adding brine, changing the water level:

Not adding brine, changing the water level:

100 gallon tank, 2 gals/min fresh water flow in, 3 gals/min of the mix flow out.

dx = (x/(100-t))3dt.

dx/x = (3/100-t)dt

Again, separable.

Adding brine, changing the water level:

Adding brine, changing the water level:

100 gallon tank, 3 gals/min brine flow in at 2lbs of salt per gallon, 2 gals/min of the mix flow out.

dx = 6dt - (x/(100+t))2dt

That doesn't look very separable to me...