Question 555617
How many liters of water must be added to 10 liters of 30% alcohol in order to produce 50 liters of 10% alcohol?
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You've limited the possibilities.
To get 50 liters, he has to add 40 liters.
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That will make the solution 6% alcohol.
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To add water to make a 10% mixture would require 20 liters of water for a total of 30 liters.  That's the most you can make with water and 10 liters of 30%.