According to a recent book I read, the following puzzle, though relatively simple and completely uncontroversial, will be answered incorrectly by more than 80% or respondents:
Each card has a single letter on one side, a single number on the other. (As is normal with cards) you can only see one side of each card. You see these 4 cards:
A F 2 7
You are asked to determine the truth of the statement “every card with a vowel on one side has an even number on the other” by flipping as few cards as possible.
Which cards should you flip?
I would like to test the claim that fewer than 20% of respondents answer correctly, so:
- Please don’t view the poll results before voting
- Please take as much time as you would like to arrive at an answer, then vote above.
- Feel free to use paper and pencil, or a computer, but please do not search the internet or any other reference.
- Please do not comment – after 30 votes have been collected or a couple of days passed, I’ll post the correct response
PS: There should be 16 possible answers, but the poll feature limited me to 10.
The results of the poll, and the correct puzzle answer, are at "'A F 2 7' puzzle survey results"
Please do not vote after visiting the results thread. You will taint the poll. Clay
Puzzle survey to confirm a published result
Re: Puzzle survey to confirm a published result
...
Poll results
