SOLUTION: I am having problems figuring out what the equation is for this problem. Paula has 400 milliliters of a solution that is 80% alcohol. She plans to dilute it so that it is only 50%

Question 408254: I am having problems figuring out what the equation is for this problem. Paula has 400 milliliters of a solution that is 80% alcohol. She plans to dilute it so that it is only 50% alcohol. How much water will she have to add in order to do this?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Paula has 400 milliliters of a solution that is 80% alcohol. She plans to dilute it so that it is only 50% alcohol. How much water will she have to add in order to do this?
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Equation:
water + water = water
0.20*400 + 1x = 0.50(400+x)
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Multiply thru by 100 to get:
20*400 + 100x = 50*400 + 50x
50x = 30*400
x = 240 ml (amt of water needed)
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Cheers,
Stan H.
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