Halcyon Daze Posted April 14, 2015 (edited) 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 No peeking at the answer! Edited April 14, 2015 by Halcyon Daze Share this post Link to post Share on other sites
Halcyon Daze Posted April 14, 2015 . . I SAID NO PEEKING!!!!!!!!!!! . Share this post Link to post Share on other sites
Halcyon Daze Posted April 14, 2015 (edited) YOU'RE A WINNER BABY!!! Edited April 14, 2015 by Halcyon Daze 1 Share this post Link to post Share on other sites
ace1928 Posted April 14, 2015 June 18Why?Only two June dates out of all other possible monthsOnly one 18 for the day out of all the other possible daysAny other day/month combo wouldnt be conclusive because others couldnt be ruled out. Share this post Link to post Share on other sites
Halcyon Daze Posted April 14, 2015 (edited) WTF That can't be right, can it?!?! LOL, keep guessing Ace! Edited April 14, 2015 by Halcyon Daze Share this post Link to post Share on other sites
zed240 Posted April 14, 2015 From this riddle I can work out that Cheryl is a bitch. 14 Share this post Link to post Share on other sites
Idon'tstudydinosaurs Posted April 14, 2015 (edited) 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 April 14, 2015 by archaeologistintraining 1 Share this post Link to post Share on other sites
DELETED ACCOUNT Posted April 14, 2015 (edited) 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 April 14, 2015 by antonsyd Share this post Link to post Share on other sites
Halcyon Daze Posted April 14, 2015 (edited) 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 Edited April 14, 2015 by Halcyon Daze 1 Share this post Link to post Share on other sites
-RC- Posted April 14, 2015 I want those 2 minutes of my life I spent reading this back. So I guess the answer is 2. 2 Share this post Link to post Share on other sites
ColinO'Scopy Posted April 14, 2015 Albert and Bernard replied in unison 'Fuck off then Cheryl' Share this post Link to post Share on other sites
wert Posted April 14, 2015 Cheryl masturbates by counting backwards from 13 minutes. She climaxes at precisely 0 seconds. Share this post Link to post Share on other sites
Seldom Posted April 14, 2015 the f did i just raed 1 Share this post Link to post Share on other sites
incognito Posted April 15, 2015 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 my brain is just lazy I guess I couldn't even read through the question Share this post Link to post Share on other sites
Distracted Posted April 15, 2015 I honestly couldn't care enough to work this out without some kind of reward whether it be material or arbitrary. 1 Share this post Link to post Share on other sites
Seldom Posted April 16, 2015 i pledge 1 arbitrary reward ^ Share this post Link to post Share on other sites