# Square Roots of Denominators and Fractions.

**URL:** <https://boards.straightdope.com/t/square-roots-of-denominators-and-fractions/355006>\
**Category:** Factual Questions\
**Created:** [May 1, 2006, 10:19pm UTC](https://boards.straightdope.com/t/square-roots-of-denominators-and-fractions/355006 "2006-05-01T22:19:58Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Jim\_B](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jim_b/32/4338_2.png) [@Jim\_B](https://boards.straightdope.com/u/Jim_B)\
**Post date:** [May 1, 2006, 10:19pm UTC](https://boards.straightdope.com/t/square-roots-of-denominators-and-fractions/355006/1 "2006-05-01T22:19:58Z")

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I remember when I was in high school they used to tell us something which still seems a little odd. When simplifying equations, we were supposed to remove square roots from denominators (and put them in the numerator) and remove fractions from radicands. No exact explanation was given for why we had to do this. We were just told leaving it there was frowned upon for some reason. Yet it doesn’t seem to make any real difference. For example, I can get square roots of fractions on my calculator with no problems.

Does anyone know what I am talking about and _why this is so_? Thank you in advance to all who reply 🙂

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**Author:** ![Cunctator](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Cunctator](https://boards.straightdope.com/u/Cunctator)\
**Post date:** [May 1, 2006, 10:38pm UTC](https://boards.straightdope.com/t/square-roots-of-denominators-and-fractions/355006/2 "2006-05-01T22:38:08Z")

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This was discussed not long ago: [link](http://boards.straightdope.com/sdmb/showthread.php?t=363730)

When I was at school using log tables, it was much easier not to have a surd in the denominator.

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**Author:** ![Mathochist](https://avatars.discourse-cdn.com/v4/letter/m/c89c15/32.png) [@Mathochist](https://boards.straightdope.com/u/Mathochist)\
**Post date:** [May 2, 2006, 7:56am UTC](https://boards.straightdope.com/t/square-roots-of-denominators-and-fractions/355006/3 "2006-05-02T07:56:56Z")

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> [@Jim B.](#):
>
> I remember when I was in high school they used to tell us something which still seems a little odd. When simplifying equations, we were supposed to remove square roots from denominators (and put them in the numerator) and remove fractions from radicands. No exact explanation was given for why we had to do this. We were just told leaving it there was frowned upon for some reason. Yet it doesn’t seem to make any real difference. For example, I can get square roots of fractions on my calculator with no problems.
> 
> Does anyone know what I am talking about and _why this is so_? Thank you in advance to all who reply 🙂

**Cunctator** ’s link is worth reading. My take is that the most important part of your post is “when I was in high school”, where algorithmic simplicity wins out over strict necessity. In theory a radical in the denominator is perfectly fine, but in practice it’s easier to manipulate expressions with “rationalized” denominators.