A Math Riddle

what would you answer

  • 25%

    Votes: 7 21.2%

  • 50%

    Votes: 16 48.5%

  • 60%

    Votes: 3 9.1%

  • 25%

    Votes: 7 21.2%
  • Total voters
    33
O

onkelmicha

Certified Hard Worker
Dec 2, 2009
2,293
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So since im like cro magnon when it comes to math so would I like to hear what some of the more educated people here would answer.

If you choose to answer this question at random, what is the chance that you will be correct.
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  • 25%
  • 50%
  • 60%
  • 25%
 


Gonna go with option B. You've got a 50% chance of being correct by choosing either A or D.
 
This question doesn't make sense, is it even valid if there are 2 choices of 25%?
 
If "D" was the only 25%, or if "E" existed and was 20%, you could choose those and be correct. Otherwise there are no correct answers.
 
my guess would be 37.5%. There is an equal probability of choosing A,B,C,D - 25% chance.

If you chose answer A or D, there is a 2/4 = 50% chance of being correct. If you choose B or C, there is a 1/4 = 25% chance of being correct.

.50(.25) + .25(.25) + .25(.25) + .5(.25) = 37.5%.

Of course, the faulty assumption is that at least one of the answers in the puzzle is correct. Since that's not the case...I don't know what the answer is. 0%?

...hopefully I get part marks for showing my work. Give me a ribbon.
 
0% would also be a contradiction. Because you would be correct while saying at the same time you have 0% chance of choosing the correct answer.
 
Philip P said:
My brain hurts.
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This quote from the wiki entry papjohn posted should clear things up ;)
One way that the paradox has been dramatised is as follows:


Suppose that every public library has to compile a catalog of all its books. The catalog is itself one of the library's books, but while some librarians include it in the catalog for completeness, others leave it out, as being self-evident.


Now imagine that all these catalogs are sent to the national library. Some of them include themselves in their listings, others do not. The national librarian compiles two master catalogs – one of all the catalogs that list themselves, and one of all those that don't.


The question is now, should these catalogs list themselves? The 'Catalog of all catalogs that list themselves' is no problem. If the librarian doesn't include it in its own listing, it is still a true catalog of those catalogs that do include themselves. If he does include it, it remains a true catalog of those that list themselves.


However, just as the librarian cannot go wrong with the first master catalog, he is doomed to fail with the second. When it comes to the 'Catalog of all catalogs that don't list themselves', the librarian cannot include it in its own listing, because then it would belong in the other catalog, that of catalogs that do include themselves. However, if the librarian leaves it out, the catalog is incomplete. Either way, it can never be a true catalog of catalogs that do not list themselves.
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