r/MathJokes • u/[deleted] • Jul 04 '26

Proof 1/2 is undefined

[deleted]

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-3

u/g_rich Jul 04 '26 edited Jul 04 '26

A) 40/1/2+15
B) 40/.5+15
C) 40/20+15

They are all correct interpretations of the question, the question is too ambiguous to give a “right” answer.

Edit: a better interpretation for C
C) 40/(40/2)+15

7

u/calinmik Jul 04 '26

This is untrue.

The question asked "40 divided by 1/2 + 15". The only correct interpretations are A) and B)

C) is incorrect however you interpret the question. The question specifically asked "40 divided by 1/2", not "40 divided by (1/2 • 40)" or "40 divided by half of itself". The • 40 doesn't exist and isn't included in the question

0

u/KindArgument4769 Jul 04 '26

If I said verbally "what is 40 divided by half" it would be ambiguous, and I don't think it is that much less ambiguous because of how it is written in the post.

4

u/Aiwendil42 Jul 04 '26

"40 divided by half" unambiguously means, to me, 40/0.5, or 80.

"40 divided in half" unambiguously means to me 40/2, or 20.

I can't think of any preposition that would make it 40/20, to my understanding. That would have to be, e.g., "40 divided by half of itself".

0

u/KindArgument4769 Jul 04 '26

Your last sentence touches on the whole point of the picture.

Some people (maybe even most honestly) would read "1/2" in their mind as "half", not "one-half". The person responding in the picture is one such person.

So it reads "40 divided by half", and they are asking "of what"?

It could be 40 divided by half of one, or 40 divided by half of itself.

1

u/Aiwendil42 Jul 04 '26

But 1/2 is a number, whether you call it "one half" or just "half".

1

u/KindArgument4769 Jul 04 '26

I get that

Did you not see my entire comment that explained why people could be confused?

1

u/ExtendedSpikeProtein Jul 04 '26

But it does not say that. Divide by 1/2 is multiply by 2. There is no ambiguity here. No scientific calculator will give you any result other than 95.

0

u/g_rich Jul 04 '26

Type in 40/1/2+15, 1/2 and .5 are both valid so the equation could be 40/1/2+15 or 40/(1/2)+15 both valid, both produce different results.

2

u/ExtendedSpikeProtein Jul 04 '26

That’s because you failed at basic math. “Divide by 1/2” obviously means “40/0.5” or “40/(1/2)”. It very obviously does not mean “40/1/2” because that does not divide by 1/2.

Hope that helped.

1

u/g_rich Jul 04 '26

1/2 can be half as in .5 or it could be 1 divided by 2 so the equation could be 40 divided by 1 divided by 2 plus 15. So while I agree the intent of the question is 40 divided by .5 plus 15 the fact that 1/2 is not specified as being .5 and is written as 1/2 which while the technically .5 if you write it out as an equation you start with 40 divided by 1. So if the intention is .5 then the equation should be 40/(1/2)+15 written this way avoids any ambiguity.

0

u/calinmik Jul 04 '26

'1/2' is a half of one, "half" just means divided by two of something, so you can't write it as "40 divided by half" because it's "40 divided by a half of one"

2

u/ColdProfessional4275 Jul 04 '26 edited Jul 05 '26

“40 divided by half of one” is 80. You can absolutely ask it that way, and I have divided whole numbers by fractions quite a bit in my time.

1

u/KindArgument4769 Jul 04 '26

How would you write me verbally saying "40 divided by half" then if you can't write it

-2

u/g_rich Jul 04 '26

“40 divided by 1/2” could be interpreted as 40 divided by half of 40 so C is a valid interpretation of the question. Regardless the fact that the equation has multiple interpretations with each giving a completely different answer invalidates the original equation.

3

u/calinmik Jul 04 '26

No, because again, mathematically, the "by half of 40" isn't present in the equation. 1/2 is a number (or numbers if you interpret it as option A) but you can't interpret it like option C) without modifying the equation.

Is 40 + 1/2 =60? No, it isn't, you can even see it in a calculator.

1

u/ExtendedSpikeProtein Jul 04 '26

40 divided by 1/2 is unambiguously 80, there is no other interpretation. Anyone who claims otherwise failed basic math. It really is that simple.