puma072806 said:Homework Statement
A chemist ran out of a 72 ml solution of 12% alcohol. All that is left in the lab is 8% alcohol and 20% alcohol. How many ml of 8% and 20% would be needed to make a 72 ml solution of 12%?
Homework Equations
The Attempt at a Solution
8x + 20y = 12
HallsofIvy said:What would x+ y represent in this situation?
Of course, if you have x ml of 8% solution then .08x (not "8x") would be the amount of alcohol in it and if you have y ml of 20% solution then .20y would be the amount of alcohol in that. So .08x+ .20y would be the amount of alcohol in the combined soltion. But that is NOT 12 or .12. .12 is the percentage of alcohol in the 72 ml solution. What do you need to multiply the .12 by to get the amount of alcohol? You can then multiply the entire equation by 100 to get rid of the decmals.
puma072806 said:Would I multiply .12 by 72 ? Which would then be 8.64
This is what I have so far.
.12 X 72=8.64
.08x + .2y=8.64
(100) .08x + .2y=8.64 (100)
8x + 20y= 864
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