SOLUTION: a 10% and a 20% salt solution are combined to make 12 gallons of 15% salt solution. How much of each strength solution is required?

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Question 452936: a 10% and a 20% salt solution are combined to make 12 gallons of 15% salt solution. How much of each strength solution is required?
Found 3 solutions by mananth, ikleyn, josgarithmetic:
Answer by mananth(16949) About Me  (Show Source):
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percent ----------------quantity
salt solution I 10---------------x lb
salt solution II20---------------12-x lb
Total 15.00% ---------------- 12

10x+20(12-x)=15 *12
10x+240-20x=180
10x-20x=180-240
-10x=-60
/-10
x=6lb ---10.00%
6lb---- 20.00%

Answer by ikleyn(53614) About Me  (Show Source):
You can put this solution on YOUR website!
.

In his post, @mananth treats ingredients in lb, which unit represents pounds.

It is incorrect. The unit to use in this problem is gallons.

So, lb at each and every appearance here must be replaced by gallons.



Answer by josgarithmetic(39730) About Me  (Show Source):
You can put this solution on YOUR website!
6 gallons of each. Arithmetic steps should not be necessary, since 15% is exactly in the middle of 10 and 20.