Question 620192
How many gallons of an 80% antifreeze solution must be mixed with 100 gallons of 30% antifreeze to get a mixture that is 70% antifreeze?
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Equation:
anti + anti = anti
0.80x + 0.30*100 = 0.70*(x+100)
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80x + 30*100 = 70x + 70*100
10x = 40*100
x  = 400 gallons (amt. of 80% solution to add)
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Cheers,
Stan H.