{"id":23867,"date":"2015-04-15T00:00:00","date_gmt":"2015-04-15T00:00:00","guid":{"rendered":"https:\/\/cms.fiveaa.com.au\/uncategorized\/maths-problem-for-14-year-olds-stumps-the-world\/"},"modified":"2015-04-15T00:00:00","modified_gmt":"2015-04-15T00:00:00","slug":"maths-problem-for-14-year-olds-stumps-the-world","status":"publish","type":"post","link":"https:\/\/cms.fiveaa.com.au\/news\/maths-problem-for-14-year-olds-stumps-the-world\/","title":{"rendered":"Maths problem for 14 year olds stumps the world"},"content":{"rendered":"

After this question was set for 14 year old Maths students in Singapore, it’s become a worldwide head-scratcher.<\/h3>\n

Thousands of people baffled… and we’ve just joined them.<\/p>\n

THE TEST ASKED:<\/strong><\/p>\n

Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.<\/p>\n

May 15, May 16, May 19<\/p>\n

June 17, June 18<\/p>\n

July 14, July 16<\/p>\n

August 14, August 15, August 17<\/p>\n

Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.<\/p>\n

Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too.<\/p>\n

Bernard: At first I don’t know when Cheryl’s birthday is, but I know now.<\/p>\n

Albert: Then I also know when Cheryl’s birthday is.<\/p>\n

\"\"<\/p>\n

So when is Cheryl’s birthday?<\/strong><\/p>\n

Can it be answered?<\/span><\/p>\n

Yes \u2013 and, thankfully, the answer is now out there.<\/p>\n

In case you’re still wondering…<\/p>\n

1. We know Cheryl has already told Albert the month of her birthday, and Bernard the day.<\/p>\n

2. Each of the men does not know what the other has been told.<\/p>\n

3. For Albert to be ‘certain’ that Bernard can’t know the answer – as suggested in the first statement he makes – we can deduct that the birthday is not in May or June. This is because in the months of May and June there are numbers (dates) that only occur once across the four months – namely May 19 and June 18.<\/p>\n

4. If Albert had been given May or June as the month, there is no way he could be certain that Bernard doesn’t know the birthday. Bernard, after all, might have been the number 18 or 19.<\/p>\n

5. For Albert to be ‘certain’ that Bernard doesn’t know, Albert must have been given a month that does not contain one of these ‘unique’ dates – i.e. July or August.<\/p>\n

6. Albert’s disclosure now gives Bernard the clue he needs, and says he now knows the birthday.<\/p>\n

7. Bernard only knows the number of Cheryl’s birthday, but from Albert’s statement he has now also ruled out both May and June. This is because he realises Albert has ruled out May and June because of the ‘single number’ aspect above.<\/p>\n

8. So there are now just five remaining dates – July 14, July 16, Aug 14, Aug 15, Aug 17 – and Bernard says he knows which is the birthday.<\/p>\n

9. Because he now knows the date, we can whittle it down further to three dates by ruling out the numbers that appear in duplicate.<\/p>\n

10. If Cheryl had told Bernard that her birthday fell on the 14th of the month, then he could not have worked out the date at this stage.<\/p>\n

11. However, as he states that he now knows the date, we can rule out July 14 or August 14.<\/p>\n

12. This leaves just three dates to chose from – July 16, Aug 15 and Aug 17.<\/p>\n

13. Following Bernard’s statement, Albert is then apparently able to deduce the date of Cheryl’s birthday.<\/p>\n

14. This means her birthday must be the only remaining date in the month he was originally told.<\/p>\n

15. Given that there are two dates left in August and one in July, it has to be the July date.<\/p>\n

16. So the answer is July 16.<\/p>\n

Easy… right? <\/p>\n

SEE ALSO: DANGERFIELD SPILLS THE BEANS ON PHIL WALSH<\/a><\/strong><\/p>\n

SEE ALSO: HER HUSBAND DOESN’T LOOK LIKE THIS ANYMORE!<\/a><\/strong><\/p>","protected":false},"excerpt":{"rendered":"

After this question was set for 14 year old Maths students in Singapore, it’s become a worldwide head-scratcher. Thousands of people baffled… and we’ve just joined them. THE TEST ASKED: Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible […]<\/p>\n","protected":false},"author":6,"featured_media":23868,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[144],"tags":[],"geo_market":[],"class_list":["post-23867","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"acf":[],"yoast_head":"\nMaths problem for 14 year olds stumps the world - FIVEAA<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/cms.fiveaa.com.au\/news\/maths-problem-for-14-year-olds-stumps-the-world\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Maths problem for 14 year olds stumps the world\" \/>\n<meta property=\"og:description\" content=\"After this question was set for 14 year old Maths students in Singapore, it’s become a worldwide head-scratcher. 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