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A riddle given to 14yo Maths Students


Halcyon Daze

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In case you haven't seen it yet

This riddle showed up in a maths exam for 14 year olds.

Can you do it? I did https://www.shaman-australis.com/forum/uploads/emoticons/default_smile.png

No peeking at the answer!

https://www.shaman-australis.com/forum/applications/core/interface/imageproxy/imageproxy.php?img=http://www.straitstimes.com/sites/straitstimes.com/files/20150413/math1e.jpg&key=036e75b938316e2275127b690806c62d52c131bb643c5aa827e754b89fb127a8

Edited by Halcyon Daze
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YOU'RE A WINNER BABY!!!

https://www.shaman-australis.com/forum/applications/core/interface/imageproxy/imageproxy.php?img=http://cdn.funnyhub.com/2015/jan/carlton-dance/carlton-dance03.gif&key=1e8617db6445de06e7550e7ba654caa4546231e99882a72c59f9beee12eba05e

https://www.shaman-australis.com/forum/applications/core/interface/imageproxy/imageproxy.php?img=http://gifsec.com/wp-content/uploads/GIF/2014/02/Happy-Dance-GIF.gif&key=fcc7020fec7bb8428c0634cfbef1d15df0ec447960dcb53a3e7ac73ff37ce2da

https://www.shaman-australis.com/forum/applications/core/interface/imageproxy/imageproxy.php?img=http://mashable.com/wp-content/uploads/2013/07/The-Office.gif&key=5bf66db8c9999d5528b7fb099da7305a2495b2b5bb7b1724ccebdc18b37fbedf

Edited by Halcyon Daze
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June 18

Why?

Only two June dates out of all other possible months
Only one 18 for the day out of all the other possible days
Any other day/month combo wouldnt be conclusive because others couldnt be ruled out.

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Maths exam for 14 year olds in Korea maybe.

I am guessing the trick is to, since only one knows the day and one knows the month, figure out who knows which and deduct from that.

Either way, she won't have them as friends for long...

Edited by archaeologistintraining
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Nice riddle!

Choices:

May / 15, 16, 19
June / 17, 18
July / 14, 16
August / 14, 15, 17

Albert knows that Bernard doesn't know. This means it can't be May 19 or June 18, as if Bernard knew these days (18 or 19), he would have already figured it out.

May / 15, 16, 19
June / 17, 18
July / 14, 16
August / 14, 15, 17
Bernard doesn't know to start with, but now he knows Albert definitively thinks he couldn't have known beforehand. So, he knows the month can't be May or June, as only July or August have all non-unique days.
May / 15, 16, 19
June / 17, 18
July / 14, 16
August / 14, 15, 17
For Bernhard to now know the answer, given he was only told a day, it must have been either July 16, or August 15 or 17, because if he was told 14, he couldn't be sure between July 14 and August 14.
May / 15, 16, 19
June / 17, 18
July / 14, 16
August / 14, 15, 17
Now that Albert knows Bernard has the answer, he can figure that it must have been July 16, because otherwise Bernard couldn't have been sure, as there are two choices left in August.
These kind of puzzles are called induction puzzles or common knowledge logic puzzles. Another tricky one is the Muddy Children problem.
It's crazy to think that there are many 'levels' of knowledge...
  • I know the answer. July 16.
  • Now I know that you know I know the answer.
  • Now I know that you know I know you know I know the answer.
  • Now I know that you know I know you know I know you know I know the answer.
  • Now I know that... etc., ad infinitum... whoa dude.
Edited by antonsyd
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Yep, it's quite simple when you realise you can rule out May and June right from the second half of the opening sentence. ie "I know that Bernard does not know too."

That leaves just July and August.

Bernard says "well now I know" because he knows it's 16 (of either May or July and it can't be May)

And Albert now knows for sure because He already knows it's July, and because Bernard could only know it if it was July 16 (If it was 14 then Bernard would not have been able to know).

Simple <___base_url___>/uploads/emoticons/default_smile.png

Edited by Halcyon Daze
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I want those 2 minutes of my life I spent reading this back. So I guess the answer is 2.

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Cheryl masturbates by counting backwards from 13 minutes. She climaxes at precisely 0 seconds.

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I hate it when u have to do these kinda tests before u get an interview for some jobs. My brain instantly puts it in the fuk this bs pile <___base_url___>/uploads/emoticons/default_sad.png my brain is just lazy I guess I couldn't even read through the question <___base_url___>/uploads/emoticons/default_sad.png

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