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ASF Puzzles & Conundrums Thread

Discussion in 'General Chat' started by Kauri, Nov 22, 2005.

  1. Kauri

    Kauri E/W Learner

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    Re: ASF joke thread

    Which one is bigger....A or B..? :)
     

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  2. wayneL

    wayneL Rotaredom

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    Re: ASF joke thread

    Same size?
     
  3. Kauri

    Kauri E/W Learner

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    Re: ASF joke thread

    Identical.. :)
     
  4. RichKid

    RichKid PlanYourTrade > TradeYourPlan

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    Inspired by Joe's jokes thread, this is for riddles, puzzles, conundrums and that type of thing.
     
  5. bellenuit

    bellenuit Well-Known Member

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    15mathproblem_toned-articleLarge.jpg

    The above problem has gone viral around the internet over the past few weeks, so many of you may have seen it. It just requires some straightforward logic, no math.

    Based on some of the responses I have seen, I would add the following assumptions to stop people being wrong tracked.

    1. Albert knows that Bernard has been told the day of the birthday and Bernard knows that Albert has been told the month.
    2. Each hears the statement the other makes.
    3. Both Albert and Bernard have sufficient information to make the assertions they made at the time they were made and each assertion is correct.

    Can you work out Cheryl's birthday?
     
  6. luutzu

    luutzu Well-Known Member

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    June 17.

    Because Cheryl was born under Gemini, and according to that star sign... Key Characteristics Multi-talented, thinker, talkative, social, scattered, diverse interests, loves variety and excitement, haha
     
  7. luutzu

    luutzu Well-Known Member

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    OK, not June 17.

    Don't think their answer is right either.

    I think it's August 17th.

    I read their answer and it doesn't gel with me. It might be reasonable if they both do not hear each other, but they seem to be hearing whether the other answer or not.

    ---

    My take, after reading theirs :D

    Can't be 18th or 19th else Bernard would know right away as there's only one of each those dates.

    Can't be June because Albert know about 18th or 19th not being it, so if it's June he will know it's June 17th. But Albert doesn't know.

    Bernard reason this thru, know what we're saying, so say since it can't be June, it must be August 17th because she told me it's 17th. If it's any other date, Bernard cannot now know because others have double.

    Albert then heard this so he then knows, reason Bernard wouldn't have known for sure if the date repeats (have two or more of), so it must be 17th, so he now also know it's 17th August.

    -----------

    Their reasoning:

    1. can't be 18th or 19th
    - true
    2. Can't be May or June because Albert, knowing the month, could have guessed 19th or 18th.
    - can't be June yes; but she could have told Albert it's May and there's two option left out of 19th to guess from. So even if it's May, Albert can't know for sure anyway.


    Anyway... this was for 3rd graders?
     
  8. bellenuit

    bellenuit Well-Known Member

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    Apparently Singaporean 14 year old students, but it isn't that difficult if you are in to logic puzzles.
     
  9. cynic

    cynic Well-Known Member

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    My logic tells me July 16. It seems to be the only date that enables all statements to be true.
     
  10. trainspotter

    trainspotter Well-Known Member

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    Forget about the math ... what about the grammar? How do you just "become" friends with Cheryl? I want her phone number and forget about her birthday.

    The answer is of course July 16th ;)
     
  11. luutzu

    luutzu Well-Known Member

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    How did you two get that?

    I read their reasoning but couldn't work it out to be July 16th.

    Their reason that it couldn't be May or June - because Albert would have guessed May 19th or June 18th - that doesn't make sense.

    I get that it couldn't be June because Albert just exclude the June 18th and get the June 17th if he know it's June; but if he know it's May, there's two other options left in May beside May 19th.

    To say that it can't be May or June for above reason... it must follow that it cannot be any other number either - because if it's, say 15th, then Bernard could figure out it's either 15th May or Aug etc. But he clearly couldn't knowing it's on the 16th.

    -----
    Say I'm Albert and I am told it's May. It could be 15th or 16th May... since I can't be sure, I said I don't know.

    So the fact that Albert said he doesn't know first doesn't mean that it cannot be in May.

    Now to Bernard... He heard that Albert doesn't know which mean it could not be June since June now only have one option left. So if it's June, Albert would have said he knew.

    Since 14th, 15th, 16th all have two options in each month... How could Bernard know? He could only know, since he was told the date, if that date only have one option - hence the 17th of August.


    --------

    Anyway, got news for you kids... thinking this hard is not what take you far in the world. It's who you know, how well you can brown-nosed, and your ability to take orders without question. :D [and no, I haven't ruin my children, yet]
     
  12. cynic

    cynic Well-Known Member

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    1. Albert's first statement tells us that he is able to determine (from the month given) that Bernard cannot have been told either 18 or 19 (they appear once only and would therefore be sufficient to identify the date). Hence the months in which they appear (i.e.May and June) can now be ruled out.

    2. Bernard's statement tells us that, the day number (provided by Cheryl), combined with information deduced from Albert's first statement, is sufficient to isolate the month thereby knowing the date. Given that 14 appears against both July and August those dates can now be conclusively ruled out. At this point the only remaining candidates are July 16, August 15 and 17 .

    3. Albert's final statement seals the deal!
    The only way Albert can certainly know the date after Bernard's statement is if there is only one remaining date in the month provided to Albert by Cheryl.
    August still has two remaining options (15 and 17) so the month of August can now be ruled out leaving July 16 as the only possible answer!
     
  13. cynic

    cynic Well-Known Member

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    Are you sure that's wise?

    After all Cheryl didn't provide the year of her birth!

    For all we know she could be older than Methuselah!

    And we all know how coy some women can be about their age, particularly when getting a bit long in the tooth!
     
  14. luutzu

    luutzu Well-Known Member

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    point 2 n 3 makes sense, but only if 1 is true.

    1 can't be true because while you can rule out June, you can't rule out the possibility of Cheryl's month being May.


    So we have it that Albert speak first, and he said he doesn't know. Him knowing the month, but he cannot know the day and month... why? Because after ruling out 19, 18... if it's in June Albert will know for sure. But if it's in May, it could be May 15, 16... other two months remaining all have >1 option... so knowing the month cannot lead Albert to know.

    Bernard likely rule out 18, 19... He's the second being ask... He infer from Albert that it's not June17... so of the remaining 3 months, each month have >1 option... How could Bernard be certain it's on the 16th when there are two 16th?

    So it cannot be 16 or 15, or 14... it must be the only one date that's left - 17th August.

    ----

    For the reasoning to be 16th July... it would equally be plausible that it's the 15th Aug. Because if 17th June is ruled out, as 19 and 18 is ruled out then May and June must be ruled out, so if 17th June is out then 17th Aug must also be out else Bernard will know (based on the same reasoning) etc.
     
  15. Ferret

    Ferret Well-Known Member

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    I worked out Aug 17. Re the underlined above, why do you think both May 15 and May 16 must be ruled out at this stage?
     
  16. skc

    skc Well-Known Member

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    If Albert was given May, he couldn't say that "I know that Bernard does not know" definitively. Because Albert doesn't know if Bernard was given the date "19". If Bernard was given 19 by Cheryl, it would invalidate what Albert said. If Albert was given May, he could only say "Bernard may or may not know".

    Therefore, Albert was NOT given May.

    BTW, the correct answer is

    Unfriend Cheryl unless she's really hot...;)
     
  17. Habakkuk

    Habakkuk Well-Known Member

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    This is a pure logic puzzle; no probability involved at all. It was set for 14-year olds.
    You're making it complicated with all kinds of logic errors. If you wish, I can explain it clearly, but it's been done almost to death on other sites.
    The best way to look at it is to consider the three (3) points-of-view: Albert's, Bernard's and yours. What does each person know after each statement?
     
  18. cynic

    cynic Well-Known Member

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    18 and 19 each occur once only.

    If either of these two numbers were given to Bernard by Cheryl, he would automatically be able to identify the associated month.

    However, Albert knows from the month (given by Cheryl) that it is not possible for Bernard to solely determine the birthdate (from the day number Cheryl provided).

    Hence any month featuring a day that would otherwise enable Bernard to identify the month, would render Albert's first statement invalid.

    Consequently, May and June can be excluded.

    Edit: Just noticed SKC beat me to it!
     
  19. luutzu

    luutzu Well-Known Member

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    yea... makes perfect sense, now.... but what if Albert really likes Cheryl and live in denial so just blurt out that "Bernard is a fool, there is no way he would know." :D

    Yea i'd unfriend Cheryl - if it's this hard to get her birth date, forget about the bases. But then maybe she really like them both and so were testing... now that the test has been met, there is a definite chance.
     
  20. Value Collector

    Value Collector Well-Known Member

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    If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?
     
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