Percent mixture

Question

How many liters of water must
be added to 25L of a 30% salt
solution to produce a 10%
solution?

Answer 1

Why don't we go a little further than just a hint?  Using an equation, we get .30 * 25 = x * .10  => 7.5 = x * .10  therefore, x = 7.5 / .10 = 75

The total amount of water will have to be 75 liters, thus an extra 50 liters, of fresh water, will have to be added.

 

A simpler way to do this is to realize that, since what we want is a solution which has 1/3 the concentration of salt we currently have, this will require a total amount of water 3 times what we currently have. Thus, 25 * 3 =75, and again, we have to add 50L of fresh water.

 

                                   Blake M.

Answer 2

Hints:

 

30% of 25L can be represented as

(.30)25 = 7.5

 

The amount of salt does not change

7.5 is 10% of what number?

 

This will be the total amount of the solution - keep in mind that you already have 25L of the solution, so how much water needs to be added?