Question 512049
With mixture problems you have to keep track of how much 'pure' stuff you have or need.
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60%*x + 30%*100 = 36% (x+100)
.60x + .30(100) = .36(x+100)
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multiply both sides of 100
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60x + 30(100) = 36(x+100)
60x + 3000 = 36x + 3600
24x = 600
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x = 25
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Answer: Add 25 ml of 60% acid  to 100 ml of 30% to produce 125 ml of 36% acid.
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.36*125 = 45 ml 'pure' acid
.6 * 25 = 15 ml 'pure' acid
.3 * 100 = 30 ml 'pure' acid
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Correct.
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Done.