Yea I'm stuck...HELP breakdown with answer

I have a 70% solution and a 15% solution and I am asked to make 480ml of a 30% solution. What parts of each strength will be used and what's the final volume of each needed for prescription? So this is my first question of this type so once I understand I think I can do the rest or similar ones. Thank you

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Alligation method
by: datazngirl

First you need to identify what kind of problem this is.

You need to apply the tic-tac-toe alligation method to solve this. In the middle is your desired concentration, then the top left is your highest concentration. The bottom left is the lowest concentration given. Then subtract diagonally, and take the absolute value of your answer. You will end up with:

|70| |15|
| |30| |
|15| |40|

Now set up your ratio proportion. You have 15 parts of the 70% and 40 parts of the 15%. In total there are 55 parts (40+15 parts).
This is how you get the volume of each concentration to make your 30% desired concentration.
15/55 x 480ml
40/55 x 480ml

Hope this helps.

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