Question 72598
If you need to mix 5L of fluid containing 25%alcohol and you have one that 
cotains 50%alcohol and another with 15%alcohol how much of each do you need 
to mix.
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Amt of 50% solution is "x" L; Amt of alcohol is 0.5(x)= 0.5x L
Amt of 15% solution is "5-x"L; Amt of alcohol is 0.15(5-x)= 0.75-0.15x L
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Amt of 25% mix is 5 L; amt of alcohol is (1/4)5= 1.25 L
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EQUATION:
alcohol + alcohol = 1.25
0.50x + 0.75-0.15x = 1.25
Multiply thru by 100 to get:
50x + 75 - 15x =125
35x=50
x=10/7 = 1.43 L (amt of 50% solution)
5-x=3.57 L )amt of 15% solution)

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Cheers,
Stan H.