SOLUTION: How many gallons of 70% antifreeze must be mixed with 120 gallons of 20% antifreeze to get a mixture that is 40% antifreeze?

Question 223635: How many gallons of 70% antifreeze must be mixed with 120 gallons of 20% antifreeze to get a mixture that is 40% antifreeze?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
How many gallons of 70% antifreeze must be mixed with 120 gallons of 20% antifreeze to get a mixture that is 40% antifreeze?
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Equation:
alcohol + alcohol = alcohol
0.70x + 0.20(120) = 0.40(x+120)
Multiply thru by 100 to get:
70x + 20*120 = 40x + 40*120
30x = 20*120
x = 20*4
x = 80 gallons (amt. of 70% antifreeze needed for the mixture)
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Cheers,
Stan H.
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