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-   -   For those as smart as Devonin, or those who think they are, prove yourselves! (http://www.flashflashrevolution.com/vbz/showthread.php?t=99197)

Cerulean Angel 09-7-2008 09:29 PM

For those as smart as Devonin, or those who think they are, prove yourselves!
 
So, I went to my AP physics class today and the teacher asked us a question, and he wanted our answer to be JUSTIFIED by us with specific evidence, here was the question:

Does 1 = .999...(repeating), literally as it is

I and two other people got this right out of thirty, so I want to see how many here can get it right, ready, go!

EDIT: The underscore didn't go in the right place so I had to fix it, it's .999...forever

DarknessXoXLight 09-7-2008 09:34 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
Well 1/3 = .333.
2/3 = .666.
and 3/3 = .999.
But 3/3 is 1.
So technically it does ...

Tank101 09-7-2008 09:35 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
I assume you mean .999 repeating (your repeating sign is somehow over the "D" in "Does")

I'm not that great at math, but my friend is.

bringst3hgrind (9:28:10 PM): ok
bringst3hgrind (9:28:11 PM): um
bringst3hgrind (9:28:12 PM): let
bringst3hgrind (9:28:19 PM): x = .999999 repeating
bringst3hgrind (9:28:31 PM): so
bringst3hgrind (9:28:43 PM): 10x = 9.999999999999999999
bringst3hgrind (9:28:56 PM): subtract x from both sides
bringst3hgrind (9:29:01 PM): 9x = 9
bringst3hgrind (9:29:04 PM): x = 1

Edit: ninja'd

Cerulean Angel 09-7-2008 09:36 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
waiting for more before I give out the answer, and there's more than one justification, I'm looking more for an algebraic formula or something, but that was a good way of putting it

Cerulean Angel 09-7-2008 09:37 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
Quote:

Originally Posted by Tank101 (Post 2787542)
I assume you mean .999 repeating (your repeating sign is somehow over the "D" in "Does")

I'm not that great at math, but my friend is.

bringst3hgrind (9:28:10 PM): ok
bringst3hgrind (9:28:11 PM): um
bringst3hgrind (9:28:12 PM): let
bringst3hgrind (9:28:19 PM): x = .999999 repeating
bringst3hgrind (9:28:31 PM): so
bringst3hgrind (9:28:43 PM): 10x = 9.999999999999999999
bringst3hgrind (9:28:56 PM): subtract x from both sides
bringst3hgrind (9:29:01 PM): 9x = 9
bringst3hgrind (9:29:04 PM): x = 1

Edit: ninja'd

Your friend is correct! That's how I did it, you got it right! Congrats, this thread is done already, that was quick, your friend is very smart! A lot of people refuse to believe it, but that's the right way to justify it!

The other way is true, but my teacher wanted a more solid answer

Tasselfoot 09-7-2008 09:37 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
1. ban evasion, so banned.

2. .999 does NOT equal 1. but .999... (Repeating) DOES equal 1.

proofs:

proof a:


proof b:


proof c:


there are more...
http://en.wikipedia.org/wiki/0.999...


edit: 3. this is a retardedly easy and basic and well known problem to be given out in an AP Physics class.

Go_Oilers_Go 09-7-2008 10:24 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
I also wonder what relevance this holds to Physics. I think it would be better suited to a Math class.

devonin 09-7-2008 10:42 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
I'm not good at math, why does this thread title have anything to do with me?

Squeek 09-7-2008 10:56 PM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
People think you're smart.

Logically, it doesn't. Mathematically, it does.

It makes logical people like me hate mathematical people like Tass.

This and that stupid Monty Hall problem.

devonin 09-8-2008 12:08 AM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
Monty Hall makes sense to me now.

So does the comparative size of infinities, but that one took a lot of explaining.

A lot of things which are 'true' in math are highly counterintuitive to non-mathematicians.

Tasselfoot 09-8-2008 02:11 AM

Re: For those as smart as Devonin, or those who think they are, prove yourselves!
 
I love the Monty Hall problem.


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