How many milliliters of water must be added to 300 ml of 70% alcoholic solution to make a 40% alcoholic solution?
You must add 225 mL of water.
This is a dilution problem, so we can use the dilution formula:
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Thus, you would add 225 mL of water to 300 mL of 70 % alcohol, and you would get 525 mL of 40 % alcohol.
300 mL of 70 % alcohol contains 210 mL of alcohol, and 525 mL of 40 % alcohol contains 210 mL of alcohol.