Real-Life Math -- Solution
In this question, you have to figure out how much water to mix with the 12 percent solution in order to make 1 gallon of 5 percent solution.
The calculation goes like this:
First we figure out the ratio of solution to water to get 5 percent.
Let A = 12 percent, B = 0 percent (water), C = 5 percent
Then we figure out how much 12 percent solution we need:
C - B
5 - 0 = 5 parts of the 12 percent solution
Now, we figure out how much water we need:
A - C
12 - 5 = 7 parts of the water
Now you have the answer: to make a 5 percent solution, you add in 5 parts of the 12 percent solution and 7 parts of the water.
So how much solution and how much water do you need for 1 gallon of solution?
5 parts of solution + 7 parts of water = 1 gallon
12 parts = 1 gallon
Now you need to know how much each part is.
12x = 1 gallon
x = 1 / 12
x = 0.083 gallons
So to mix up your solution you need:
5 x 0.083 gallons of the 12 percent solution = 0.415 gallons
And
7 x 0.083 gallons of water = 0.581 gallons