<PRE><B>Question 521471</B>
You need a 80% alcohol solution. On hand, you have a 320 mL of a 85% alcohol mixture. How much pure water will you need to add to obtain the desired solution?
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Equation:
alcohol + alcohol = alcohol
0.85*320 + 0*x = 0.80(320+x)
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Multiply thru by 100 to get:
85*320 + 0 = 80*320 + 80x
5*320 = 80x 
x = 20 mL (amt. of pure water needed)
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Cheers,
Stan H.
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