SOLUTION: A Cooling System In An Automobile Requires 2.5 Gallons Of A 50% Antifreeze Solution. Presently, The Sytem Has A 30% Solution. How Much Of The Present Solution Must Be Replaced With

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Question 781560: A Cooling System In An Automobile Requires 2.5 Gallons Of A 50% Antifreeze Solution. Presently, The Sytem Has A 30% Solution. How Much Of The Present Solution Must Be Replaced With Pure Antifreeze To Bring The System Up To The Recommended Concentration?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Have 30% concentration; want 50% concentration, no change in volume.
v = volume gallons of the 30% to remove and replace with pure.

%282.5%2A30-v%2A30%2Bv%2A100%29%2F2.5=50------You need to understand this equation.
%282.5%2A30%2B%28100-30%29v%29%2F2.5=50
75%2B70v=125
70v=125-75
v=50%2F70=highlight%285%2F7%29

Remove 5%2F7 of a gallon and replace with pure 100% antifreeze.