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A logical question

  1. Aug 13, 2008 #1
    fairies are small and smart.
    a creature is not smart,unless it's not serious.
    fairies are serious.

    what answer is not possible
    1.a small and serious fairy
    2.a smart creature which is not a fairy
    3.a small creature which is not serious
    4.a serious creature which is not a large and smart creature

    i don't know why they chose 1
    as the correct answer
  2. jcsd
  3. Aug 13, 2008 #2


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    1 could not possibly be the correct answer, since those two properties of fairies are given.
  4. Aug 13, 2008 #3


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    I lie. It is 1.

    Fairies are a contradiction.

    By (1), they're Smart. (within blue and green)
    But, by (2), if it's Smart, it has to be Serious (blue is within red)

    So, answer 1a proposes a fairy that is inside Smart (blue), but outside Not Serious (red) (because (3) fairies are serious)

    Heh. Conclusion: Fairies don't exist. Clever.

    Attached Files:

    Last edited: Aug 13, 2008
  5. Aug 13, 2008 #4
    can you please post a link to your attached photo
    i was told that i am not privileged to view it
    Last edited: Aug 13, 2008
  6. Aug 13, 2008 #5
    i was told also that fairies are serious
    why didnt you maked this in the graph
    there should be a fairy dot in a serious circle

    why didnt you do it?
    Last edited: Aug 13, 2008
  7. Aug 13, 2008 #6


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    Neither am I. It's a bug.

    You can view the pic by looging out and then viewing it.
  8. Aug 13, 2008 #7


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    The point is that there is no where that one can put a dot that represents fairies.

    No single point can satisfy all given criteria.
  9. Aug 14, 2008 #8
    so this questions has an error in it
  10. Aug 14, 2008 #9
    Not true. The data only says that all dumb (not smart) creatures are also playful (not serious). It says nothing about smart creatures. They can be serious or playful. Now, if there are supposed to be some "All" somewhere in the data, then that's a different story.
  11. Aug 14, 2008 #10


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    That's not quite what it says.

    Well, let's see if we can get the set diagram correct. Do you see any flaws in mine?
  12. Aug 14, 2008 #11
    So, there's arguably no actual error in the question-- although you could argue that there is. I like the playful/serious and dumb/smart comparisons since they simplify the wording. That is, "not smart" == "dumb", and "not serious" == "playful". See how it affects the ease of understanding in the puzzle:

    1. fairies are small and smart.
    2. a creature is dumb, unless it's playful.
    3. fairies are serious.

    Now it's much easier to untangle the logic in #2. It's saying that ALL serious creatures are necessarily dumb. The only way a creature can avoid being dumb is by being playful. Now look at fairies. They're supposedly smart and serious! But if #2 is correct, then a fairy goes against the rule. Hence, the implication is that there's no such thing as fairies-- if fairies don't exist, then no rules are broken. Fairies might as well be small and big, or smart and dumb. Since none exist, there's arguably no contradiction.

  13. Aug 14, 2008 #12
    thank i understood that
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