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Not an Alligation ?

by Sharon
(Missouri)

How many mL of water should be added to 2500mL of 83% (v/v)alcohol to prepare 50% (v/v) alcohol?


Reply (by Keith)

Although you technically could use an alligation grid to work this problem, it would be a disaster and probably take up a whole sheet of paper. Alligations are best used when you have a higher and lower concentration and know what your desired volume is, which is what's missing here.

So, a better way to do this is with basic algebra, using the formula C1V1=C2V2. You can do this one in about 6 lines on paper. Here's your first line:

(2500)(.83) + (X)(.00) = (2500+X)(.50)

Solve for X

@ @ @ @ @ @ @ @ @ @ @ @ @ @
If you can spare 12 minutes,
watch this brief tutorial
I posted to YouTube
on Basic Algebra.

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