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## #1 2013-01-21 21:39:12

kjames
Guest

### mixture problem

How much copper and how much magnesium should be added to 200 lbs of an alloy containing 20% copper and 40% magnesium to produce an alloy containing 24%copper and 50% magnesium?

## #2 2013-01-21 22:38:33

phrontister
Real Member

Offline

### Re: mixture problem

Hi kjames,

Sorry, but I'm tied up doing something else for quite a while, and so I can only give a quick answer that isn't exact (it's a decimal approximation), and as I got it with Excel's Goal Seek I can't give the method you probably want, either.

Here's what I got:

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

## #3 2013-01-21 22:47:42

kjames
Guest

### Re: mixture problem

Thanks for giving time in answering my question but can somebody else show me the solution so that I can learn how to do it..thank you!

## #4 2013-01-21 23:47:33

bobbym

Offline

### Re: mixture problem

Hi;

Let c be the amount of copper to be added and m the amount of magnesium to be added

c = 440 / 13, m = 960 / 13

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #5 2013-01-22 10:37:23

phrontister
Real Member

Offline

### Re: mixture problem

Hi,

Nice and compact, Bobby! I didn't think of going that way.

This is how I've done it:

Initially...
Copper      =  20% of 200 lbs  =   40 lbs
Magnesium =  40% of 200 lbs  =   80 lbs
Other         =  40% of 200 lbs  =   80 lbs
Totals        = 100%                 = 200 lbs

Copper        =   24% of x lbs
Magnesium  =   40% of x lbs
Other          =   26% of x lbs, ∴ x = 80/26% lbs
Total           = 100%

Copper added      = 24% of x = (24*80/26)-40 lbs = (960/13)-40   = 440/13
Magnesium added = 50% of x = (50*80/26)-80 lbs = (2000/13)-80 = 960/13

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

## #6 2013-01-22 10:49:22

bobbym

Offline

### Re: mixture problem

Hi;

There are many ways to solve a problem. That should be enough to make the OP happy!

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.