SOLUTION: what is the minimum amount of pure alcohol that must be added to a 24 liters of a 20 percent alcohol solution to obtain a mixture that is at least of 30 percent alcohol.

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Question 884223: what is the minimum amount of pure alcohol that must be added to a 24 liters of a 20 percent alcohol solution to obtain a mixture that is at least of 30 percent alcohol.
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
The total alcohol is the sum of the initial amount plus what you add
You are asked to find the point where the total volume is 30% alcohol.
You start with a 24liter volume that is 20% and then add in 100%
Let the 100% volume you add be y
so
+%280.20%2A24%29+%2B+y+=+0.3%2824%2By%29
4.8+%2B+y+=+9.6+%2B+0.3y
y+-+0.3y+=+9.6+-+4.8
0.7y+=+4.8
y+=+4.8+%2F+0.7
y+=+6.857 liters so at least that much