# Thread: Solving for an unknown variable

1. ## Solving for an unknown variable

Hi

How best can I approach this question?

A solution containing 45% water is mixed with another solution containing 10% bromine. If the chemist needs 30 liters of the mixture, how many liters of each solution are needed to make a 34.5% water/bromine solution?

Let x= water and y= the salt solution

"If the chemist needs 30 liters of the mixture"
x + y = 30 ...is that right?

2. ## Re: Solving for an unknown variable

Originally Posted by KayPee
A solution containing 45% water is mixed with another solution containing 10% bromine. If the chemist needs 30 liters of the mixture, how many liters of each solution are needed to make a 34.5% water/bromine solution?
Let x= water and y= the salt solution
"If the chemist needs 30 liters of the mixture"
x + y = 30 ...is that right?
Easier this way: let w = water ; then bromine = 30 - w
Code:
   w   @  .45
30-w   @  .10
====      ====
30   @  .345
Can you turn that into an equation, then solve for w?