SOLUTION: Biology students at Salem College are preparing a solution of isopropyl alcohol to use in preserving specimens. One of the students, Max, needs to mix up 10 liters of 66% solution.

Question 1128218: Biology students at Salem College are preparing a solution of isopropyl alcohol to use in preserving specimens. One of the students, Max, needs to mix up 10 liters of 66% solution. If the lab has 72% isopropyl alcohol solution and 42% isopropyl alcohol solution, how much of each should Max mix together?
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
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mix up 10 liters of 66% solution. If the lab has 72% isopropyl alcohol solution and 42% isopropyl alcohol solution, how much of each
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x of the 72%

8 of the 72% and 2 of the 42%
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!

Here is a quick way to solve mixture problems like this without the formal algebra. If you understand this method, it will get you to the answer much faster than algebra.

66 is 6 away from 72 and 24 away from 42.
The ratio of 6 and 24 is 6:24 or 1:4; that means the ingredients must be mixed in the ratio 4:1.
A ratio of 4:1 to make 10 liters means 8 liters of one and 2 liters of the other.
Since 66% is closer to 72% than to 42%, you need 8 liters of the 72% and 2 liters of the 42%.
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