Mixture Problems: 8% salt soln mixed w/ 4 oz 20% soln

[Kat]

I am reviewing for a college algebra class, I am having a problem remembering how to set up a mixture problem.

Problem: A mixtures containing 8% salt is to be mixed with 4 ounces of a mixture that is 20% salt, in order to obtain a solution that is 12% salt. How much of the first solution is to be used?

I used to be able to do these well, but can't seem to remember how to set it up. Can anyone help? Thanks!

KAT

[stapel_eliz]

Problem: A mixtures containing 8% salt is to be mixed with 4 ounces of a mixture that is 20% salt, in order to obtain a solution that is 12% salt. How much of the first solution is to be used?

I used to be able to do these well, but can't seem to remember how to set it up.

To review how to set up and solve "mixture" exercises, try here. Once you have studied the lesson in the link, the following will make sense:

+-----+------+------+--------+
+-----| oz.  |  %   |  oz.   |
+-----| soln | salt |  salt  |
+-----+------+------+--------+
| 1st |      | 0.08 |        |
+-----+------+------+--------+
| 2nd |  4   | 0.20 | 4(0.2) |
+-----+------+------+--------+
| mix |      | 0.12 |        |
+-----+------+------+--------+

Pick a variable for the amount you need to find. Fill in the blanks. Then add down (as the lesson explains) to find your equation. Solve for your variable.

If you get stuck, please reply showing your work and reasoning so far. Thank you!

Eliz.

[DAiv]

Problem: A mixtures containing 8% salt is to be mixed with 4 ounces of a mixture that is 20% salt, in order to obtain a solution that is 12% salt. How much of the first solution is to be used?

+-----+------+------+--------+
+-----| oz.  |  %   |  oz.   |
+-----| soln | salt |  salt  |
+-----+------+------+--------+
| 1st |      | 0.04 |        |
+-----+------+------+--------+

Shouldn't that 0.04 be 0.08?

DAiv

[stapel_eliz]

Shouldn't that 0.04 be 0.08?

Oops!

I've corrected the table above. Thank you!