SOLUTION: How many quarts of pure antifreeze must be added to 7 quarts of a 50% antifreeze solution to obtain a 60% antifreeze solution? Thanks!

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Question 648119: How many quarts of pure antifreeze must be added to 7 quarts of a 50% antifreeze solution to obtain a 60% antifreeze solution?
Thanks!
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
How many quarts of pure antifreeze must be added to 7 quarts of a 50% antifreeze solution to obtain a 60% antifreeze solution?
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Equation:
alcohol + alcohol = alcohol
0.50*7 + x = 0.60*(7+x)
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Multiply thru by 100 to get:
50*7 + 100x = 60*7 + 60x
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40x = 10*7
x = (1/4)7
x = 1.75 quarts (amt. of pure antifreeze needed)
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Cheers,
Stan H.
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