Poll

does it

yes
no
math joke

Author Topic: the ultimate question: does 0.9999... equal 1  (Read 1691 times)

Okay, so is this
0.999... (infinite 9s here) ...999
or is it
0.999... (infinite 9s here, with no literal end)

literal no end


Here's an idea...

Let's get rid of the decimal system.

In the set of real numbers, 0.9999... = 1.
In the set of hyperreals where you can have numbers infinitely close to but not equal to 1, 0.999... is not a valid representation of a number as far as I'm aware.

So yes, it's equal.
If you want some ideas of why, here are a couple proofs:
x = 0.9999...
10x = 9.9999...
10x - x = 9.0
9x = 9
x = 1

1/9 = 0.1111...
2/9 = 0.2222...
3/9 = 0.3333...
...
7/9 = 0.7777...
8/9 = 0.8888...
So 9/9 = 0.9999..., and 9/9 = 1.

Easy solution.
.999... - 1 = What?
0.000....
Never has a 1 or higher, so it gets simplified to 0.