# How can .9999etc. be considered equal to 1 in math?

**URL:** <https://boards.straightdope.com/t/how-can-9999etc-be-considered-equal-to-1-in-math/179164>\
**Category:** Factual Questions\
**Created:** [June 2, 2003, 5:48pm UTC](https://boards.straightdope.com/t/how-can-9999etc-be-considered-equal-to-1-in-math/179164 "2003-06-02T17:48:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![don\_willard](https://avatars.discourse-cdn.com/v4/letter/d/a88e57/32.png) [@don\_willard](https://boards.straightdope.com/u/don_willard)\
**Post date:** [June 2, 2003, 5:48pm UTC](https://boards.straightdope.com/t/how-can-9999etc-be-considered-equal-to-1-in-math/179164/1 "2003-06-02T17:48:39Z")

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I always read in mathematics books how  
.999and 9 forever actually equals 1, and they don’t mean because you just round it off, either, they really mean it literally equals 1. I can’t understand the thinking here. Also, 2) does this also imply that .8888 etc. equals 9? and so on.  
I’m not interested in the practical implications, but in the theory of why they say .999999999  
etc. has to be considered equal to 1.

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**Author:** ![don\_willard](https://avatars.discourse-cdn.com/v4/letter/d/a88e57/32.png) [@don\_willard](https://boards.straightdope.com/u/don_willard)\
**Post date:** [June 2, 2003, 5:50pm UTC](https://boards.straightdope.com/t/how-can-9999etc-be-considered-equal-to-1-in-math/179164/2 "2003-06-02T17:50:37Z")

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Eeeeee.eee! I didn’t know that someone else has taken this up. I just posted this and then going to gen questions I see below my post there is a whole several pages on this. I will look into it now.

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**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\
**Post date:** [June 2, 2003, 6:18pm UTC](https://boards.straightdope.com/t/how-can-9999etc-be-considered-equal-to-1-in-math/179164/3 "2003-06-02T18:18:16Z")

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No problem, **don** , I’ll close this and refer replies to [Why doesn’t .9999~ = 1?](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=187902)

**DrMatrix** - GQ Moderator