Algebra Mixture Problems Help

[AbhiKap]

Hey I am working on these mixture problems and I understand it mostly. However, what I do not understand is the following: Sometimes the answer you find for a given problem by doing the chart method is simply x (whatever value you found for x) Sometimes, however, the question asks more and you have to subtract something or do something with the value found for x. Like sometimes the question might be, "How many pounds" or something. How do you know if the answer is simply the value found for x or if you have to subtract or something. If you do have to do something, how do you know if it is subtracting or adding?

I hope I was clear enough and if I need to rephrase the paragraph just let me know.

Thanks, Help is greatly appreciated.

 

[AbhiKap]

No, you were not (well, not to me antway).
Try again; provide examples...

ok. For example:

Mr. Acosta works in the lab at a pharmaceutical company. He needs to make 30 liters of a 23% acid solution to test a new product. His supplier only ships a 12% and a 27% solution. Mr. Acosta decides to make the 23% solution by mixing the 12% solution with the 27% solution. How much of the 12% solution will Mr. Acosta need to use?

In this problem, after finding the answer, Is the answer just what we find for x or what? Like after solving this with the chart method, I got 8 liters. Is that correct or do we have to do something else with the x such as subtract or something?

Thanks, Help is greatly appreciated.

 

[AbhiKap]

OK: when solving for x, what you get for x is what
YOU declared x to represent.

The question in that problem is:
How much of the 12% solution will Mr. Acosta need to use?

It is good practice to let the unknown represent what's in the
question; that way, you get the answer right away:
let x = quantity of 12% solution
(then 30 - x is by default the quantity of 27% solution).
And solving will give x = 8, so you are CORRECT...good work!

Now, say we went the other way:
let x = quantity of 27% solution
(then 30 - x is by default the quantity of 12% solution).
Solving will give x = 22 liters of 27% solution
Since question asks for 12% solution, you now need
to go another step: 12% solution = 30 - 22 = 8.

That's it...don't try and over-analyse it

Asking questions as you do indicates that you are
seriously trying to learn...a VERY good thing: keep it up !

Thanks a lot Denis, I really really appreciate the help. Thanks.