SOLUTION: This is a question I missed from a recent test. I'm beating my head against the wall trying to figure this out. Thanks in advance for any help you can provide. How much of a 7

Algebra ->  Customizable Word Problem Solvers  -> Mixtures -> SOLUTION: This is a question I missed from a recent test. I'm beating my head against the wall trying to figure this out. Thanks in advance for any help you can provide. How much of a 7      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



Question 127817: This is a question I missed from a recent test. I'm beating my head against the wall trying to figure this out. Thanks in advance for any help you can provide.
How much of a 75% chemical solution must be mixed with a 25% solution to make 10 liters of a 40% solution?

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
We want to end up with a 10 liters of 40% solution. That means that of the 10 liters, 4 liters are the chemical, and the rest is something else. To make this mixture, we want to mix x liters of 75% solution with enough 25% solution to make the full 10 liters. So the amount of 25% solution must be 10-x liters.

The 75% solution has .75x liters of chemical, and the 25% solution has .25%2810-x%29 liters of chemical. These two quantities must add up to the 4 liters that make up the amount of chemical in the final solution (geez, that sounds ominous!).

So:
.75x%2B.25%2810-x%29=4

.75x-.25x%2B2.5=4

.5x=4-2.5=1.5

x=3

So there are 3 liters of 75% solution, meaning that there are 7 liters of 25% solution.

Check:
3%2A.75=2.25
7%2A.25=1.75

2.25%2B1.75=4