<PRE><B>Question 894881</B>
a pharmacist needs to strengthen a 20% alcohol solution so that it contains 36% alcohol. how much pure alcohol should be added to 240 milliliters of the 20% solution?
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Equation:
Quantity:: x + y = 240 ml
Alcohol:: 0.20x + y = 0.36*240
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Subtract the lower equation 
from the upper equation to get ::
0.80x = 0.64*240
x = 192 ml (amt. of 20% solution needed)
240-x = 48 ml (amt. of pure alcohol needed)
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Cheers,
Stan H.
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