SOLUTION: How much pure acid should be mixed with 2 gallons of an 80% acid solution in order to get a 90% acid solution. To get 90% acid solution , you need ( ) gallons of pure acid.

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Question 526664: How much pure acid should be mixed with 2 gallons of an 80% acid solution in order to get a 90% acid solution.
To get 90% acid solution , you need ( ) gallons of pure acid.
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
You have 2 gal. @ 80%, which is .8*2 = 1.6 gal. of pure acid.
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You need add 'x' gallons of 100% pure acid to make a 90% solution.
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.8*2 + 1*x = .9(2+x)
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1.6 + x = 1.8 + .9x
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multiply by 10 to eliminate decimals
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16 + 10x = 18 + 9x
x = 2
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Answer: Add 2 gallons of pure acid to 2 gallons of 80% acid to make a 90% acid solution.
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Check the answer:
.8*2 = 1.6 gal of pure acid in the original 2 gal.
1.6 + 2 = 3.6 gal of pure acid in the final solution.
3.6/4 * 100 = 90%.
Correct.
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Done.