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Background: I am a French educated person.

My old math teacher keeps posting some small and funny riddles, here's one of his:

The next equation is correct:

11111=0

Can you prove it?

Note: Hopefully, when the answer is revealed, the tags will have been sufficient (Sorry if I missed any).

bobble
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Paul Karam
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10 Answers10

70

Could it be that

$11111 = 11, 111$
which, in French, is pronounced "onze, cent onze".

To a speaker, this sounds very much like "onze sans t-onze" which would mean "eleven without eleven" and could justifiably be said to be zero.

NB @Maiaux has pointed out in their answer that the intention may be the whole phrase "onze mille cent onze" to sound like "onze mille sans onze" or "11000 without 11" which could be read as 000. I would say this is worth an upvote too.

hexomino
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    There's a French "who's on first" routine about a man ordering shirts (chemises) over the phone from a slightly deaf shop clerk. When the man is asked how many he wants, he replies: "sept" (7) "Pardon?" "J'ai dit 'sept'" (I said 7) "Ah. Dix-sept. Merci" (Oh, 17. Thanks.) "Non! Sans dix. Sept" "Cent dix-sept?" "Sept! Sans dix! Sept!" "Sept cent dix-sept?" and so on. – Hugh Meyers Apr 18 '18 at 14:20
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    You're 95% right, but can you explain it using the whole number? I mean without adding a , yourself. – Paul Karam Apr 18 '18 at 14:21
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    @PaulKaram I think I see what you mean. My French is not brilliant, unfortunately, but I will try to find a phrase that fits. – hexomino Apr 18 '18 at 14:46
  • @PaulKaram the comma is completely irrelevant. Thousands separators are included for the convenience of the reader. The reading does not change with or without the comma separator. All the more because the comma is actually the decimal separator in french: hexomino is wrong (using english separators)[1], it should be with a space. Regardless, the first statement stands true. - - - - - - [1]: I think that for most romance languages, the comma is a decimal separator. – Mindwin Remember Monica Apr 18 '18 at 18:35
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    Shouldn’t it be “onze mille cent onze” in French? This sounds as “onze mille sans onze”, which could be interpreted as “mille” (1000), “11000-11=10989” or perhaps “(11-11)*1000=0”... – Maiaux Apr 18 '18 at 19:32
  • @Maiaux You're into something there... Just think if you wrote "onze mille sans onze" literally, in numbers, what do you get? – Paul Karam Apr 18 '18 at 20:03
  • @PaulKaram well, I’d get something like “000”, which is 11000 without the 11... – Maiaux Apr 18 '18 at 20:07
  • @Maiaux Which is equal to? – Paul Karam Apr 18 '18 at 20:07
  • @PaulKaram yep, 0, the intended answer – Maiaux Apr 18 '18 at 20:08
  • Ah, I see, I thought there was some word I was missing. I see the intention now, will edit shortly. – hexomino Apr 18 '18 at 21:15
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    @hexomino In your answer, you wrote that this sounds like "onze sans t-onze", but I think the "t-" part should be removed, since, AFAIK, the "t" in "cent" is silent and there's no liaison when the following word is "onze" – Maiaux Apr 19 '18 at 15:33
39

I would look at it from this perspective.

11111 are 5 lines.
In morse, 5 lines (dashes) means 0

PL457
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  • Interesting , but I am sorry, this is not the right answer. – Paul Karam Apr 18 '18 at 11:59
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    Since we're talking about morse, how about this: The 0 represents a morse who crossed a footbridge (the =) to leave a river (the 11111). ;-) – Alex Apr 20 '18 at 08:32
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I'll follow the suggestion given by the OP. So:

"11111" in French reads as "onze mille cent onze", which sounds exactly as "onze mille sans onze" (11000 without 11).

Therefore we have

"000"

which comes from

"11000" without "11"

and of course

"000" means 0

Maiaux
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19

It might be that :

Your math teacher is also doing programming as part of his work and is using a ones' complement system. 11111 is a signed integer composed of 5 bits, which is equal to -0 in decimal which is 0, thus 11111 = 0 . See the wikipedia entry with a signed integer composed of 8 bits

Betcheg
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7

I think the answer is:

The teacher asked the question "How many contours the digits on the left surround?", to which the answer is 0. For example if there was a number 8 on the left the answer would be 2.

rhsquared
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4

I remember a question like this from my Programming Teacher, i hope this isn't a duplicate from rhsquared answer, if so i am very sorry.

It looked like an equation but the Number after "=" was just the number of enclosed spaces before the "=".

So 11111 has 0 enclosed spaces and 84141 for example 4 enclosed spaces

If this does not solve it, i am very excited to see the solution in the future.

Wazzzabii
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4

How about this:

11111 is in French "un un un un un", which sounds like the noise you make while shaking your head, indicating "no", or "nothing". Therefore 0.

Robin
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With a little help from hexomino’s answer ;)

I think that:

‘Un onze cent onze’ (one eleven-hundred eleven) sounds like ‘un onze sans onze’, translating to ‘an eleven without eleven’, which is 0.

Max
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0

A remark rather than an answer, maybe this version is a little less contorted, although slightly more dialectal:

1111 = 0 says the French teacher.

Indeed, exactly as in English you can pronounce 1111 "eleven hundred eleven", you can say "onze cent onze" in French as an alternative to "mille cent onze". Then, same as above, "onze cent onze" sounds exactly as "onze sans onze", i.e. "eleven without eleven".

Joce
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-1

Using JavaScript,

2.999999999999999999 === 3

Therefore,

11111 === 0

Code Whisperer
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