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Aug. 19, 2010 - With a translation of Beri, Smile informs you that...
sciences mathematiques

Infinite number

0.9999999… (with an infinite amount of 9) equals 1.


Details:

Doubting ? Here is the mathematical proof:


1/3 = 0.333333...
Statement A: 3 x (1/3) = 3 x 0.333333...
Statement B: 3 x (1/3) = 1
A implies 3 x 0.333333... = 0.999999...
A = B implies 0.999999... = 1

Sources:

2 = 4.
Other mathematical proofs can be found in the commentaries on the french version of this DYK.

Spincredible! - Spitiful.


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# (0) wfherschy - June 24, 2011 - 03:45
wfherschy

This is not true…think about it. If there is an infinite number of 9s, that means that the string of 9s goes on forever – and though we can round it up for theoretical purposes it is not a literally equality.

 
Well said!    --    Bah.

# (0) Dauby - June 24, 2011 - 10:32
Dauby

In order to preserve the team’s health, we advise you to take a look on the french version of this DYK and its (numerous) comments.

 
Well said!    --    Bah.

# (0) tokogod - July 19, 2011 - 00:05
tokogod

I knew that since I was 13

 
Well said!    --    Bah.


# (0) BloodyT - Nov. 27, 2011 - 15:03
BloodyT

this proof given isn’t very good, as all would need argued is 1/3 simply cant be truly expressed in decimal form and 0.3333~ is just the closest interpretation… the proof i tend to use is:
.999999~ * 10=9.999999~
9.9999~ – .9999999~ = 9 (truncating the decimals off)
however none of these proofs are truly proof, cause one could argue that 9.9999999~ represents 9.999~ – 0.00000~9(IE 1 decimal place shy of infinity)

however it should just be accepted as true, because there are no ‘ways’ to get .3333333~(aside from assuming 1/3 actually does equal it, or starting with it, or another repeating decimal)... there is no harm in using it, but to some (including computers), it makes things easier…

I’ve ran through at-least 20 different ‘proofs’, seeing the logic behind them none actually convincing me anything beyond accept it because it doesn’t ‘break’ Our math..

 
Well said!    --    Bah.

# (0) mansuetus - Nov. 29, 2011 - 16:26
mansuetus

this proof given isn’t very good

Indeed : the point was to have something “easy to read”. A nicer proof would be “if the two numbers weren’t the same number, there should exist one given number separating them”.

Or this “trivial when you have learnt limits” :

0. 99999999… = Lim (x—>+oo) 1 – 1/(10^x) = 1

(and your maths teacher would have beaten you up when you have written Lim (whatever) ~ = (something) : Limit equals )

 
Well said!    --    Bah.

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