Probability Puzzle

[KaiRu]

 

[Shantanu Kumar]

B?

 

[Tsotne]

The answer itself defines the correct answer: None is the correct answer if you randomly pick from all the 4 answers.

1 in 4 chance is 25% but because 25% is repeated two times there is a 50% chance that that answer will be picked from the selection. But if you get 25% then the answer is wrong, and if you choose 50% then your answer will be wrong because there is only a 25% chance of choosing 50%. And if you choose 0% then your answer is wrong as well. If 0% was the correct answer then the chances would again be 25% making 0% - the wrong answer. The answer is such: the random selection is to be made out of only the first 2 answers and not of all 4. It does not state that you have to choose randomly among all 4 answers.
By only randomly selecting either A or B you have reduced it to a 50% chance of getting the correct answer and so B(50%) is the correct answer.

 

[Sushant]

B

 

[AlexandreB]

It cannot be B, because you have 1/4=25% chance to pick B so 50% cannot be the answer. Cannot be A or D neither, because there's a 50% chance of picking them, hence 25% would be wrong. Thus, as Tsotne put it, there's no good answer.

 

[Freakonometrics]

The funny thing is, that after a bit of reasoning, I come to the conclusion that this is not a multiple choice question. If you chop up the question into two parts you'll see this.

Edit: Pretty sure it should be zero, as:
P(.25)=.5
P(.5)=.25
P(.6)=.25

Even if C is 0 then:
P(0)=.25

Therefore the chance is 0. In addition, the chance is zero for every C.

Edit2: I just googled the question, seems to be a lot of debate on this. Apparently no-one really seems to agree.

 

[lordvid]

Assuming the correct answer is one of the three possible answer (25%, 50%, 60%)....which are all equally probable at being the correct answer:

If you choose an answer at random, you have prob. of 2/4 = 0.5 of choosing 25%, 1/4 of choosing 50%, 1/4 of choosing 60%.

So the probability of having the right answer being chosen at random is: 1/2*1/3 + 1/4*1/3 + 1/4*1/3 = 1/3

 

[Adrián Facchi]

This reminds me to the self-reference(ish) Gödel incompleteness theorem.

 

[lordvid]

This reminds me to the self-reference(ish) Gödel incompleteness theorem.

Hahaha...I would have thought something like this was from "Alice in Wonderland"...

I can see the hookah-smoking caterpillar asking this question to Alice.
Alice: "But what is the question?"
Caterpillar: "That is the question."
Alice: "I'm afraid I don't understand. What is the question?"
Caterpillar: "I've told you, young lady, that is the question."
March Hare: "I don't have time for this nonsense. I'm late, I'm late! She'll have my head if I'm late..."