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Does .9999 repeating 1?

If so please give REAL proofs
title is supposed to have = sign

is .9999999999... ( repeating ) = 1?

January 23, 2013

17 Comments • Newest first

DxidunnoxD

It does my math teacher showed the class but I don't remember how

Reply January 24, 2013
ParamountPoster

[quote=xSuperNova]This is still...?[/quote]

This is still what? o.o

Reply January 24, 2013
Zunoku

[url=http://www.youtube.com/watch?v=wsOXvQn3JuE]Hi.[/url]

Reply January 24, 2013
Alana55

I always think of it like this:
1/3 = .3333333333333
2/3 = .666666666
1 = 3/3 = .999999999
So 1 = .999999999
Le gasp!~

Also, we can do this using algebra.
Say x=0.999999
Therefore, 10x=9.999999
~Solve the system of equations by subtracting them from eachother
~~~~~>10x - x = 9.99999 - 0.999999
~~~~~~~~>9x = 9
~~~~~~~~~>x = 1

Reply January 24, 2013
alexwee

[quote=fraddddBS]No I'm not. I simply substituted "0.444..." for "x", like it was equal to in the first place.

Have you never used substitution or something?[/quote]

probably hundreds of times more than you did lol
and you're looking at the wrong thing
i was commenting on the way you did the subtraction of 10x-x=9x and not 4x
lol....

Reply January 24, 2013
alexwee

[quote=xSuperNova]I'm sorry if I wasn't clear, let me explain line by line:

x = 0.444...
10x = 4.444...
Nothing wrong with these

10x - x = 4
Still good
4x = 4
Turns out that 10x - x is actually equal to 9x, not 4x, so correct is
9x = 4
x = 4/9

Thus, you can apply the same method for an algebraic proof that "0.999..." is equal to one.[/quote]

frad you're retarded lol

Reply January 24, 2013
tiesandbowties

i think of it like an asymptote. it never reaches 1.

Reply January 24, 2013
uOnPeriod

[quote=gamemage3]this would what we mathematicians call circular argument.
how do you know 1/3 = .33333333333?

also @ above
whos to say, that
x = .999999999
10x = 9.999999999999

you're multiplying a real number to something that might not even be a real number? the operation cross can only be used between 2 numbers in the same field, and it must be defined clearly.

Assume we can represent numbers as a sum of infinite decimals.
ln2 = 1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + 1/7 - 1/8 + 1/9 ....
multiply both sides by 2 to get
2ln2 = 2 - 1 + 2/3 - 1/2 + 2/5 - 1/3 + 2/7 - 1/4 + 2/9 - 1/5

recollect terms with same denominator
2ln2 = (2-1) - (1/2) + (2/3-1/3) - 1/4 + (2/5 - 1/5) - 1/6 +....

2ln2 = 1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + 1/7 - 1/8 + 1/9 ....
ln2 = 2ln2
1=2

contradiction
therefore numbers and infinite decimals are not the same[/quote]
If you're a mathematician work it out yourself, stop showing off and asking basil.

Reply January 23, 2013
ParamountPoster

[quote=Penguinland]No, and this is why

Write .9 as a fraction. It is 9/10, so if you had one object and cut it into 10 pieces, you'd have 1/10 left over when you took away .9 of it.

Next, write .99 as a fraction. It is 99/100. An object cut into 100 pieces would have 1/100 left over when you took away .99 of it.

Try this for .999. Fraction is 999/1000. As you can see, the more 9's you add the smaller the remainder gets.

So, if you are willing to write a very very long string of .9999999.... you would get closer and closer to the number being equal to 1.0. In fact, you can get as close as you want, no matter how close you'd like to be. However you would always, and I mean always, have a tiny bit left over.[/quote]

You say 1>0.999... but by how much?

Reply January 23, 2013
ParamountPoster

For the convergence theorem, if we have an infinite series in the form sum(Cr^n) where the absolute value of r < 1, the series converges to Cr/(1-r)

0.999... = 9(1/10)^1 + 9(1/10)^2 + 9(1/10)^3+...
Since r<1, the series converges.

9(1/10)/(1-(1/10))=(9/10)/(9/10)=1

Reply January 23, 2013
alexwee

no because it will never reach 1

Reply January 23, 2013
CyanLime

It's very close to 1 but not quite one.
As my teachers say to me all the time, don't over-think things.

Reply January 23, 2013
gamemage3

[quote=uOnPeriod]Use mathematical logic to figure it out.
3 thirds of one = 1
A third = .333333
3 times .333333 = .9999999
....[/quote]

this would what we mathematicians call circular argument.
how do you know 1/3 = .33333333333?

also @ above
whos to say, that
x = .999999999
10x = 9.999999999999

you're multiplying a real number to something that might not even be a real number? the operation cross can only be used between 2 numbers in the same field, and it must be defined clearly.

Assume we can represent numbers as a sum of infinite decimals.
ln2 = 1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + 1/7 - 1/8 + 1/9 ....
multiply both sides by 2 to get
2ln2 = 2 - 1 + 2/3 - 1/2 + 2/5 - 1/3 + 2/7 - 1/4 + 2/9 - 1/5

recollect terms with same denominator
2ln2 = (2-1) - (1/2) + (2/3-1/3) - 1/4 + (2/5 - 1/5) - 1/6 +....

2ln2 = 1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + 1/7 - 1/8 + 1/9 ....
ln2 = 2ln2
1=2

contradiction
therefore numbers and infinite decimals are not the same

Reply January 23, 2013 - edited
uOnPeriod

[quote=gamemage3]this doesn't prove anything lol[/quote]
Use mathematical logic to figure it out.
3 thirds of one = 1
A third = .333333
3 times .333333 = .9999999
....

Reply January 23, 2013 - edited
gamemage3

[quote=uOnPeriod]1/3=.333
3/3=1
3x.333333=.99999
So on.[/quote]

this doesn't prove anything lol

Reply January 23, 2013 - edited
uOnPeriod

1/3=.333
3/3=1
3x.333333=.99999
So on.

Reply January 23, 2013 - edited
scorpio989

1>.99

Reply January 23, 2013 - edited