math
posted by elisa on .
A 5% alcohol solution is mixed with 15% alcohol solution to make a 25mlof a 9% solution. How much of each alcohol solution is used?

Let x be the number of ml of the 5% solution and y be the number of moles of the 9% solution.
0.09 * 25 = 0.05*x + 0.15y (alcohol content)
x + y = 25 (total volume)
Substitute 25x for y in the first equation and solve for x.
2.25 = 0.05 x + 0.15(25x) = 3.75 0.10x
etc.