

ipe Elite user 442 Posts 
If you choose an answer to this question at random, what is the probability that you will be correct?
A) 25% B) 50% C) 0% D) 25%
What would a real mindreader do?

landmark Inner circle within a triangle 5015 Posts 
"this question " is illdefined.
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Scott Cram Inner circle 2677 Posts 
The choices defat each other in a nontransitive cycle (think rock/paper/scissors, where none of the choices are always the best), so none of the answers can be chosen at random with the correct probability.

landmark Inner circle within a triangle 5015 Posts 
Imagine this were not a multiple choice question. Rather than asking the probability of answering the question, ask what is the correct answer.
If it is answerable then there is some probability >0 of being correct if answering at random; if not answerable, then the P=0. There is no way to distinguish between the two cases.
Click here to get Gerald Deutsch's Perverse Magic: The First Sixteen Years
All proceeds to Open Heart Magic charity. 
ipe Elite user 442 Posts 
Quote:
On Nov 3, 2018, landmark wrote: What if the options would be: A) 25% B) 50% C) This question is illdefined D) 25%
What would a real mindreader do?

ipe Elite user 442 Posts 
Quote:
On Nov 3, 2018, Scott Cram wrote: If you cannot choose the correct answer, so 0% is the correct answer; but you can choose "0%" from the multiple options available.
What would a real mindreader do?

landmark Inner circle within a triangle 5015 Posts 
Choice C (illdefined) case is not an answer; it is a statement about the nature of the question.It could just as well be replaced by "I like this question."
Click here to get Gerald Deutsch's Perverse Magic: The First Sixteen Years
All proceeds to Open Heart Magic charity. 
ipe Elite user 442 Posts 
Landmark, I agree with you, I was just in the role of puzzleproposer.
What would a real mindreader do?

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