Question 271287
How many liters of a 40% antifreeze solution must be mixed with 5 liters of a 70% antifreeze solution to make a mixture that is 60% antifreeze? 
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Equation:
alcohol + alcohol = alcohol
0.40x + 0.70*5 = 0.60(x+5)
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Multiply thru by 100
40x + 70*5 = 60x + 60*5
-20x = -10*5
x = 2.5 liters (amt. of 40% solution needed in the mixture)
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Cheers,
Stan H.