Question

A scientist mixes water (containing no salt) with a solution that contains 30% salt. She wants to obtain 180 ounces of a mixture that is 15% salt. How many ounces of water and how many ounces of the 30% salt solution should she use?

Answer 1

water : 90 ounces

salt solution: 90 ounces

Explanation:

Call w the amount of water and call the solution containing 30% salt.

We want to get 180 ounces of a mixture with 15% salt.

So:

The amount of mixture will be:

`w + s = 180`

the amount of salt will be

`0w + 0.3s = 180 * 0.15`

`0.3s = 27`

`s = 90\ ounces`

Now we substitute the value of s in the first equation and solve for w

`w + 90 = 180`

`w = 90\ ounces`