I don't even know what serial dilution is, so you got one up on me, chicky! Other than that it looks like you are talking about some sort of ratios, I'm clueless.
See, know don't you feel smarter??
Of course...now I feel a little dumber...heh.
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| Math question https://gladerebooted.net/viewtopic.php?f=2&t=6348 |
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| Author: | Kirra [ Sun May 22, 2011 3:42 am ] |
| Post subject: | Math question |
I suck at math... Serial dilution question. Does a 1:2 of a 1:10 make a 1:20? thus you have to multiple the answer by 20 to get the result? And how do you make dilutions..I don't get how to make a 1:10 any other way than 1 part in 9 parts. I know probably super simple for you all. |
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| Author: | LadyKate [ Sun May 22, 2011 7:18 am ] |
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I don't even know what serial dilution is, so you got one up on me, chicky! Other than that it looks like you are talking about some sort of ratios, I'm clueless. See, know don't you feel smarter?? Of course...now I feel a little dumber...heh.
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| Author: | NephyrS [ Sun May 22, 2011 9:23 am ] |
| Post subject: | |
Yes, that will give you a 1:20 dilution. Just depends somewhat on how you're writing your ratios. 1:2 can either be construed as taking 1 part and diluting it with another part... Or it can be construed as taking one part and diluting it with 2 parts of a second solution. Usually only seems to be a problem with the lower ratios, though... If you understand which you're talking about, it's not a big deal. Other than 1 and 9? You can do 2 and 18, 3 and 27, etc. You could also do a serial dilution to make 1:10... A 1:2 dilution followed by a 1:5 dilution. But 1 and 9 is the easiest way. |
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| Author: | Corolinth [ Sun May 22, 2011 10:13 am ] |
| Post subject: | Re: |
NephyrS wrote: Just depends somewhat on how you're writing your ratios. 1:2 can either be construed as taking 1 part and diluting it with another part... Or it can be construed as taking one part and diluting it with 2 parts of a second solution. While I have no doubt that this is true, and people do write dilutions this way, one of those would be incorrect notation. Mathematical notation does not have homonyms.Kirra, the : and / symbols mean exactly the same thing. You're being asked to multiply fractions. If it helps you, rewrite the problem. 1/2 * 1/10 = 1/20 Is that true? More importantly, do you remember how to do it? |
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| Author: | Shelgeyr [ Sun May 22, 2011 12:23 pm ] |
| Post subject: | |
Interesting, so 1:10 is a "one in ten" and not a "one to ten" ratio? |
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| Author: | Lex Luthor [ Sun May 22, 2011 1:10 pm ] |
| Post subject: | Re: Math question |
| Author: | Corolinth [ Sun May 22, 2011 1:13 pm ] |
| Post subject: | Re: Math question |
For the latter, the potential mistake comes in misinterpreting what the "ten" is referring to. "One part salt to every ten parts of the solution as a whole" would carry the same meaning as "one in ten." The problem with the meaning of "one part to every ten parts of the other stuff" would arise when you have a mixture that involves more than two components. Take a pitcher of Kool-Aid. You have water, sugar, and Kool-Aid mix. You could compare sugar to "other stuff" but that would be a bit misleading when the "other stuff" is a mixture itself. This doesn't rule out someone using 1:10 in the manner of "one part sugar to every ten parts of other stuff" (making the overall concentration of sugar 1/11), and as I said, I'm quite sure it's used that way. I wouldn't be surprised to find that it's the more common of the two. It's just not the correct notation. A ratio is not "like a fraction" nor is it "related to a fraction." A ratio is a fraction. |
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| Author: | NephyrS [ Sun May 22, 2011 9:38 pm ] |
| Post subject: | |
Exactly. If you have A and B, does 1:2 mean 1 A to 2 B, or does it mean 1 part A to make 2 parts total? It's just something to make clear when you're talking it through with someone else. While one (I'm sure) is correct, I've seen peer reviewed papers use either method. And honestly, it seems to be in large part relating to the "size" of the ratio. Commonly, in lab books, you'd do a 50% dilution as "1:1".... But you'd write a 10% dilution as "1:10", or a 1% dilution as "1:100".... There's an obvious discrepancy there, but it happens, a lot. The former is assumed to mean 1 part A to 1 part B, while the latter is assumed to mean 1 part A in 10 parts total. The latter is the "correct" notation, but the former is often used for "common" dilutions. 1:1, 1:2, 1:3, 2:3, etc. |
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| Author: | Kirra [ Mon May 23, 2011 3:18 am ] |
| Post subject: | |
Hugs Coro! It makes sense to me, finally. |
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| Author: | Corolinth [ Mon May 23, 2011 3:50 am ] |
| Post subject: | Re: Math question |
The reason for the discrepancy is twofold: 1) Chemistry and Biology departments are sufficiently removed from pure mathematics that there is a tendency to forget they are still governed by it. 2) The brain does not fully understand numbers greater than 10. You're willing to try and be fancy when you've got a single digit number, but once you run out of fingers for the denominator you will gladly let established mathematical procedure take over. Still, I find it amusing that a branch of science that likes to beat rules for significant figures into students' heads would play fast and loose with how they express a fraction. |
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| Author: | Rafael [ Mon May 23, 2011 9:36 pm ] |
| Post subject: | Re: Math question |
Sweet Jesus, not sig figs. |
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