alcohol solution?

Question

How many ml (milliliters) of a 40 percent alcohol solution must be mixed with a 70 percent alcohol solution to obtain 30 ml of a 52 percent alcohol solution.

Answer 1

Analysis: The amount of alcohol in the desired solution is equal to the amount of alcohol you take from the 40% AND the amount of alcohol of 70%. Also, expect that the volume of the 40% solution must be greater than the volume of the 70% solution in order to even get a 52% final solution. (Think what would happen otherwise)

Also if x is the volume of the 40% then to get a final solution of 30 ml, then the volume of 70% solution is (30 - x). Putting it all together,

.40x + (30-x) (.70) = 30 x .52

Doing the algebra you should get x = volume = 18 mL of 40%

You can check your work by checking the volume of 70% if they add up to 30 mL.