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

[Cerulean Angel]

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]

Well 1/3 = .333.
2/3 = .666.
and 3/3 = .999.
But 3/3 is 1.
So technically it does ...

[Tank101]

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]

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]

Originally Posted by Tank101

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]

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]

I also wonder what relevance this holds to Physics. I think it would be better suited to a Math class.

[devonin]

I'm not good at math, why does this thread title have anything to do with me?

[Squeek]

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]

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]

I love the Monty Hall problem.