this post was submitted on 06 May 2025
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Science Memes

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[–] [email protected] 17 points 4 days ago

You can never answer this question correctly. If the correct answer is 25% there's a 50% chance you guess correctly but that would make the 25% wrong.

But if the answer is the 50% then it implies that 25% is correct which implies that 50% is wrong.

We reach a contradiction for both 25% and 50% making the correct answer to make the whole statement truthy 0%.

[–] [email protected] 155 points 5 days ago (12 children)

B.

This is a multiple choice test. Once you eliminate three answers, you pick the fourth answer and move on to the next question. It can't be A, C, or D, for reasons that I understand. There's a non-zero chance that it's B for a reason that I don't understand.

If there is no correct answer, then there's no point hemming and hawing about it.

B. Final answer.

[–] [email protected] 61 points 5 days ago

I love this, it shows how being good at (multiple choice) tests doesn't mean you're good at the topic. I'm not good at tests because my country's education system priorities understanding and problem solving. That's why we fail at PISA

[–] [email protected] 21 points 5 days ago

You think like I do. Bet you test well.

[–] [email protected] 9 points 5 days ago (1 children)

Entertaining response but I disagree.

I'm going to say that unless you're allowed to select more than one answer, the correct answer is 25%. That's either a or d.

By doing something other than guessing randomly (seeing that 1 in 4 is 25% and that this answer appears twice), you now have a 50% chance of getting the answer correct. However, that doesn't change the premise that 1 in 4 answers is correct. It's still 25%, a or d.

[–] [email protected] 16 points 5 days ago (4 children)

That's an interesting perspective. The odds of correctly guessing any multiple choice question with four answers should be 25%. But that assumes no duplicate answers, so I still say that's wrong.

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[–] [email protected] 25 points 4 days ago* (last edited 4 days ago) (3 children)

This can also be used a great example of proof by contradiction: There is no correct answer in the options. Proof: Assume there was a correct answer in the options. Then it must be either 25%, 50% or 60%. Now we make a case distinction.

(A) Assume it was 25. Then there would be two of four correct options yielding in a probability of 50%. Therefore 50 must be the correct answer. -> contradiction.

(B) Assume it was 50. Then there would be one of four correct options yielding in a probability of 25%. Therefore the answer is 25. -> contradiction.

(C) Assume it was 60%. Since only 0,1,2,3 or 4 of the answers can be correct the probability of choosing the right answer must be one of 0% 25% 50% 75% or 100%. -> contradiction.

Because of (A), (B) and (C), it cannot be 25, 50% or 60%. -> contradiction.

[–] [email protected] 2 points 4 days ago

Cheeky answer - the correct answer is a superposition of 25% and 50%, thus you answer it as a multiple choice question

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[–] [email protected] 95 points 5 days ago (10 children)

This is a self-referential paradox — a classic logic puzzle designed to be tricky. Let’s break it down:

Step-by-step analysis:

  1. How many choices? There are 4 possible answers, so if we pick one randomly, the chance of picking any specific one is 1 in 4 = 25%.

  2. How many answers say “25%”? Two.

  3. That means the probability of randomly choosing an answer that says “25%” is 2 in 4 = 50%.

  4. But if the correct answer is 50%, then only one option says “50%” — which is (c). So the probability of picking it at random is 1 in 4 = 25%, contradicting the idea that 50% is correct.

  5. If the correct answer is 25%, then two options say that — a and d. So the chance of picking one of those at random is 50%, not 25% — again a contradiction.

  6. Similarly, if 60% is correct (only one option), then the chance of picking it randomly is 25%, which again makes it incorrect.

Conclusion: Any choice leads to a contradiction. This is a self-referential paradox, meaning the question breaks logical consistency. There is no consistent correct answer.

[–] [email protected] 183 points 5 days ago (21 children)
[–] [email protected] 79 points 5 days ago (5 children)

haha yeah, I knew it at the "let's break it down:"
I was like.. I know this voice....

[–] [email protected] 20 points 5 days ago

"Conclusion:" was the final nail in the coffin

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[–] [email protected] 16 points 5 days ago

Got it right though

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[–] [email protected] 14 points 5 days ago (1 children)

^dontthinkaboutitdontthinkaboutitdontthinkaboutit^

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[–] [email protected] 58 points 5 days ago (3 children)

The question is malformed and the correct answer isn't listed in the multiple choices. Therefore the correct answer is 0%

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[–] [email protected] 43 points 5 days ago (1 children)

This is a conundrum wrapped in a turducken, swaddled in nesting dolls.

[–] [email protected] 11 points 5 days ago (1 children)

lol chill out there buddy it is only self-referential once. maybe twice.

[–] [email protected] 11 points 5 days ago (1 children)

I'm not certain, I think it's an infinite loop.

I.E. If the answer is 25%, you have a 50% chance, if the answer is 50%, you have a 25% chance, if the answer is 25%, you have a 50% chance...

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[–] [email protected] 28 points 5 days ago (1 children)

It's probably graded by a computer, and a) or d) is a fake answer, since the automated system doesn't support multiple right answers.

I'm going to go with 25% chance if picking random, and a 50% chance if picking between a) and d).
If it's graded by a human, the correct answer is f) + u)

[–] resting_parrot 11 points 5 days ago

Many systems do allow multiple correct answers.

[–] [email protected] 34 points 5 days ago (4 children)

It's 0%, because 0% isn't on the list and therefore you have no chance of picking it. It's the only answer consistent with itself. All other chances cause a kind of paradox-loop.

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[–] [email protected] 36 points 5 days ago

This is a paradox, and I don't think there is a correct answer, at least not as a letter choice. The correct answer is to explain the paradox.

[–] brown567 9 points 4 days ago (1 children)

0%

The only winning move is not to choose

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[–] [email protected] 23 points 5 days ago (2 children)
[–] [email protected] 8 points 5 days ago (5 children)
[–] [email protected] 12 points 5 days ago

how many roads must a man walk down?

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[–] [email protected] 10 points 5 days ago* (last edited 5 days ago) (2 children)

If you're choosing the answer, then there is 100% chance of being correct. Since none of these answers is 100%, the chance is 0%.

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[–] [email protected] 21 points 5 days ago (1 children)

C, which means A or D, which means C, which means...

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[–] [email protected] 10 points 5 days ago

Thanks for making me laugh all alone in my car before heading in to work. I wish I could give you an award. Cheers!

[–] [email protected] 19 points 5 days ago

This seems like a version of the Liar paradox. Assume "this statement is false" is true. Is the statement true or false?

There are a bunch of ways to break the paradox, but they all require using a system that doesn't allow it to exist. For example, a system where truth is a percentage so a statement being 50% true is allowed.

For this question, one way to break the paradox would be to say that multiple choice answers must all be unique and repeated answers are ignored. Using that rule, this question only has the answers a) 25%, b) 60%, and c) 50%, and none of them are correct. There's a 0% chance of getting the correct answer.

[–] [email protected] 10 points 5 days ago (1 children)

What's the correct value if the answer is not picked at random but the test takers can choose freely?

[–] [email protected] 8 points 5 days ago

All answers are correct then.

[–] [email protected] 11 points 5 days ago

Paradoxes aside, if you're given multiple choices without the guarantee that any of them are correct, you can't assign a chance of picking the right one at random anyway.

[–] [email protected] 11 points 5 days ago* (last edited 5 days ago)

If you suppose a multiple choice test MUST ONLY have one correct answer:

  1. Eliminate duplicate 25% answers

  2. You are left with 60% and 50% as potential answers to this question.

  3. C is the answer

If you were to actually select an answer at random to this question while believing the above, you would have a 50% chance of answering 25%.

It is obvious to postulate that: for all multiple choice questions with no duplicate answers, there is a 25% chance of selecting the correct answer.

However as you can see, in order to integrate the answer being C with the question itself, we have to destroy the constraints of the solution and treat the duplicate 25% answers as one sum correct answer.

Do you choose to see the multiple choice answer space as an expression of the infinite space of potential free form answers? Was the answer to the question itself an expression of multiple choice probability or was it the answer from the free form answer space condensed into the multiple choice answer space?

The question demonstrates arriving at different answers between inductive and deductive reasoning. The answer depends on whether we are taking the answers and working backwards or taking the question and working forwards. The question itself forces the inductive reasoning strategy to falter at the duplicate answers, leading to deductive reasoning being the remaining strategy. Some may choose to say "there is no answer" in the presence of needing to answer a question that only has an answer because we are forced to pick one option, and otherwise would be invalid. Some may choose to point out it is obviously a paradox.

[–] [email protected] 11 points 5 days ago* (last edited 5 days ago) (1 children)

The answer is not available. The answer is 0 Percent. Each answer, if chosen, would be incorrect. If 0% was an answer, it would be the correct one despite being a 25% chance. Of course, if one 25% was there, that would be the correct answer.

[–] [email protected] 11 points 5 days ago (7 children)

But if you did randomly choose the 0% option, you'd be correct. So if one of the possible answers was 0% the correct answer would be 25%.

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