Monday, April 13, 2015

P5 Maths question - When is Cheryl's birthday?




Here’s a supposedly P5 logic question going viral on Facebook that will melt your brain
PHOTO: Here’s a supposedly P5 logic question going viral on Facebook that will melt your brain
Posted by Jonathan Lim on 12 April 2015
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqMVK7Bogj40Lw3NDaYhGdBWdrsr_-QSh4A4NO9tfABNUZUacSvFXcE9YcCxu1fBJjZdgm6JN2B-zTKHsXGrGIvFa4Q1m7w3LEKt1XasAPSsnlclEv-jlQQolpkd17kBeNJFlJ-N8_fm0/s1600/trick-question.jpg
http://cdn.mothership.sg/wp-content/uploads/2015/04/trick-question.jpg
http://mothership.sg/2015/04/heres-a-supposedly-p5-logic-question-going-viral-on-facebook-that-will-melt-your-brain/


This logic was shared by a MediaCorp Channel 8 presenter Kenneth (江坚文 Jiāng jiān wén) [https://www.facebook.com/kennethjianwenz/photos/a.173663129479243.1073741827.167504136761809/385751114937109/?type=1&theater] on Facebook on Saturday 11 Apr.
 

In his Facebook post he said “This question causes a debate with my wife …. and its a P5 question. #trickquestion” [https://www.facebook.com/hashtag/trickquestion]
 
It is not known whether this is really a Primary 5 question or if it came from Singapore, but more importantly, can you solve the question?

Answer:
Table posted by Stephanie Ng Wan Jing
Texts (explanations) posted by Jun Cai
 

Here’s a supposedly P5 logic question going viral on Facebook that will melt your brain
PHOTO: P5 logic question
Posted by Jonathan Lim on 12 April 2015
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqMVK7Bogj40Lw3NDaYhGdBWdrsr_-QSh4A4NO9tfABNUZUacSvFXcE9YcCxu1fBJjZdgm6JN2B-zTKHsXGrGIvFa4Q1m7w3LEKt1XasAPSsnlclEv-jlQQolpkd17kBeNJFlJ-N8_fm0/s1600/trick-question.jpg 
http://cdn.mothership.sg/wp-content/uploads/2015/04/trick-question.jpg
http://mothership.sg/2015/04/heres-a-supposedly-p5-logic-question-going-viral-on-facebook-that-will-melt-your-brain/


July 16 is the only possible answer
1) Albert: I don't know when Cheryl's birthday is, but l know that Bernard does not know too.
A knows B confirm don't know the date, which means A wasn't told May or June because May and June both have an unique identifier (5/19 and 6/18) ie. If B was told 19 or 18 the entire Condition 1 is wrong.

Table-1.jpg

 
2) Bernard: At first I did not know when Cheryl's birthday is, but I know now.
We are left with July to August. B is now confident of his answer, so his Date must be unique, thus eliminating 7/14 and 8/14.

Table-3.jpg


3) Albert: Then I also know when Cheryl's birthday is.
A says he now knows the answer, because July is the only unique (There are two August dates, left)

Table-3.jpg


Posted by Jonathan Lim on 12 April 2015



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