1. ## salt solution problem

How many gallons of water must be mixed with 5 gal of 20% salt solution to make a 16% salt solution?

I put 5 over x and .2 over .16 and came up with 1.25 gal, which is the correct answer. I need to know if this is the correct way to work the problem so that I can use it later.

2. Originally Posted by tigersblood
How many gallons of water must be mixed with 5 gal of 20% salt solution to make a 16% salt solution?

I put 5 over x and .2 over .16 and came up with 1.25 gal, which is the correct answer. I need to know if this is the correct way to work the problem so that I can use it later.
Shouldn't it be 5 gal + 1,25 gal?

I may have misunderstood you, but the total should be 6,25 gal i think.

3. Yes, the total is 6.25, but the question asks how much you should add. I've got the answer, I just need to know if I have the work correct. Should I cross multiply?

4. Hello, tigersblood!

How many gallons of water must be mixed with 5 gal of 20% salt solution
to make a 16% salt solution?
I would equate the amounts of water in the mixture.

We have 5 gallons of solution which is 80% water: .$\displaystyle 4$ gallons of water.
. . We will add $\displaystyle x$ gallons of water.
The mixture will contain: .$\displaystyle x + 4$ gallons of water.

The mixture will be $\displaystyle x+4$ gallons of solution which is 84% water.
. . It has: .$\displaystyle 0.84(x + 4)$ gallons of water.

We just expressed the final amount of water in two ways.

. . There is our equation! . . . .$\displaystyle x + 4 \:=\:0.84(x + 4)$

Now solve for $\displaystyle x$.