SOLUTION: Doreen is a chemist. She needs to prepare 36 ounces of a 13% hydrochloric acid solution. find the amount of 18% solution and amount of 9% solution she should mix to get the soluti

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Question 836291: Doreen is a chemist. She needs to prepare 36 ounces of a 13% hydrochloric acid solution. find the amount of 18% solution and amount of 9% solution she should mix to get the solution...How do I solve this??? Please help me.
Found 2 solutions by nerdybill, josgarithmetic:
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
Doreen is a chemist. She needs to prepare 36 ounces of a 13% hydrochloric acid solution. find the amount of 18% solution and amount of 9% solution she should mix to get the solution.
.
Let x = amount (ounces) of 18% solution
then
36-x = amount (ounces) of 9% solution
.
.18x + .09(36-x) = .13(36)
.18x + 3.24-.09x = 4.68
.09x + 3.24 = 4.68
.09x = 1.44
x = 16 ounces of 18% solution
.
amount of 9% solution:
36-x = 36-18 = 18 ounces

Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
"prepare 36 ounces", means mass or weight.

Let u = ounces of 13%
Let v = ounces of 18%

%2813u%2B18v%29%2F36=9 and u%2Bv=36

See the lesson through profile for how that works.
"Mixing two concentrations for known amount of mixture"