Firebox Card: Number 123: Difference between revisions
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TheBozzball (talk | contribs) (Alternate (maybe simpler) explanation.) |
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<pre> | <pre> | ||
Between all the distractions and parties at university | Between all the distractions and parties at university, I did manage to fit in a few | ||
experimental psychology lectures. One of the most interesting things | experimental psychology lectures. One of the most interesting things I learned was how | ||
at heart, people | at heart, people aren't as logical as they think. Try this problem: | ||
Each of these cards has a letter (A or K) on one side and a number (2 or 7) on the reverse. | Each of these cards has a letter (A or K) on one side and a number (2 or 7) on the reverse. | ||
If | If I told you there was a rule stating that a card with A on one side will have a 2 on the | ||
reverse, which two cards would you turn over to find out if the rule was true | reverse, which two cards would you turn over to find out if the rule was true? | ||
</pre> | </pre> | ||
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</pre> | </pre> | ||
The answer is A and | The answer is A and 7. [[image:green_123.jpg|thumb|Pack of Cards]] | ||
Some people guess the answer is A and 2. The logical statement of the problem can be phrased "an A on one side implies there will be a 2 on the other." People who get the answer wrong also presume the converse is true, that "a 2 on one side implies there will be an A on the other." This is not the case; therefore the 2 does not need to be checked. Another way to see this is that the statement can be phrased "no card has an A on one side and a 7 on the other side". | |||
Latest revision as of 15:57, 4 December 2005
Illogical
From the firebox advert. The card on the top of the advert contains the following text:
Between all the distractions and parties at university, I did manage to fit in a few experimental psychology lectures. One of the most interesting things I learned was how at heart, people aren't as logical as they think. Try this problem: Each of these cards has a letter (A or K) on one side and a number (2 or 7) on the reverse. If I told you there was a rule stating that a card with A on one side will have a 2 on the reverse, which two cards would you turn over to find out if the rule was true?
The cards displayed on the card are
A K 2 7
The answer is A and 7.
Some people guess the answer is A and 2. The logical statement of the problem can be phrased "an A on one side implies there will be a 2 on the other." People who get the answer wrong also presume the converse is true, that "a 2 on one side implies there will be an A on the other." This is not the case; therefore the 2 does not need to be checked. Another way to see this is that the statement can be phrased "no card has an A on one side and a 7 on the other side".
