SOLUTION: Amanda wants to make 8 gal. of a 20% saline solution by mixing together a 56% saline solution and a 8% saline solution. How much of each solution must she use?

Question 803145: Amanda wants to make 8 gal. of a 20% saline solution by mixing together a 56% saline solution and a 8% saline solution. How much of each solution must she use?
Found 2 solutions by josgarithmetic, Alan3354:
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
I really want to respond with a solution, but 56% saline or salt will NOT happen. Amanda does NOT have 56% saline. You have been given a very bad example, but what you want to do is probably something like this:

u = how much low concentration saline to use, 8%
v = how much high concentration saline to use, 56%?
8 gallons is how much 20% saline wanted

and
... and you would solve for u and v.

Note too that densities would be very significant for any realistic problem of this type, and you would need to account for densities, since you seem to have w/w or w/v percent concentrations
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Amanda wants to make 8 gal. of a 20% saline solution by mixing together a 56% saline solution and a 8% saline solution. How much of each solution must she use?
================
e = amount of 8%
f = amount of 56%
---
e+ f = 8 (total solution)
8e + 56f = 20*8 (total saline)
---
e+ f = 8
e + 7f = 20
------------ Subtract
-6f = -12
f = 2
e = 6
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