<PRE><B>Question 741162</B>
Elise wants to make a 61% alcohol solution. She has already poured 3 gal. of a 40% alcohol solution into a beaker. How many gal. of a 70% alcohol solution must she add to this to create the desired mixture? 
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Equation:
alch + alch = alch
0.40*3 + 0.70x = 0.61(3+x)
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40*3 + 70x = 61*3 + 61x
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9x = 21*3
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x = 7 gallons (amt of 70% solution needed)
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Cheers,
Stan H.</PRE>