Singapore Math Problem

Are you smarter than a Singaporean 5th grader?  You might not be.  But this Singaporean math problem will not tell you the answer -- to whether you are smarter than a Singaporean 5th grader. The video WILL tell you the answer to the math problem.

For those of you who consider the rest of this text TL;WNR (Too long; Will not read), click on the link after this paragraph.  The link will take you to the video. The video is about 30 MB big.

	http://smarturl.it/S-poreMathPblmVid


For those of you still with me ...

I will call this math problem The Cheryl Problem.  Because Cheryl is a character in the problem.  And because if the events occurred in real life, Cheryl would BE the problem.  To translate a Singlish expression:  Act cute.  Fail cute.

The host of a TV show in Singapore wrote on Facebook that The Cheryl Problem came from a 5th-grade math test.  It did not.  The Cheryl Problem came from the test for the 2015 Asia International Mathematical Olympiad.  Which is not as exclusive as it sounds.  It is not strictly for Asian countries.  England is in it.  And despite the name, participation is not restricted as in the real Olympics.  If a school participates in the Mathematical Olympiad, the school is supposed to let take the test any of its students who pay 20 Singapore dollars (S$20).  That is about 15 US dollars (US$15).  A student in a participating country who does not take the test through his school can still take the test on own.  It will cost more.  S$30 (about US$22.50) instead of S$20.  Not exactly the cost of sending an athlete to the real Olympics.

While the test does not try to assess all students, or even half, it does aim to be a useful measure for the top 40%.  There is a different test for each grade.  Some of the problems appear on tests for more than one grade. The Cheryl Problem appeared on the 2015 tests for basically 9th and 10th grade students.  I say 'basically' because a lot of people say 'basically' for no reason.  And I want to look as dumb as they do.  No.  Not in this case.  I say 'basically' because which test level a student takes depends not only on the schoolyear he is in, but on the number of schoolyears in the education system he is in.  In Singapore the public schools have 11 schoolyears after Kindergarten.  Generously to American students, the oldest Mathematical Olympians receiving The Cheryl Problem would have been equivalent to 11th grade American students.  The oldest Mathematical Olympians would not have been the oldest high school math students in Singapore.

However, the problems on the Mathematical Olympiad tests are numbered in approximate order of difficulty.  The Cheryl Problem was the 24th of 25 problems.  The hardest problems on a Mathematical Olympiad test for a grade level are designed for the top fraction of a percent of math students at that grade level.  For The Cheryl Problem, the top fraction of a percent of 10th-grade math students.  The Cheryl Problem is a hard problem.  Not a problem for a 5th-grade class.  In any country.

The math tutor in the video does a pretty good job.  Until the last step.  I thought she was unclear about reducing 3 possible dates to 1 date.  The video was a segment of a TV news broadcast.  Maybe the tutor would have been clearer unconstrained by the length of the segment.  I think it helps to break The Cheryl Problem into a sequence of information disclosures.  Then consider each disclosure from 3 points of view

	1) What Albert knows after the disclosure and what he can figure out

	2) What Bernard knows after the disclosure and what he can figure out

	3) What a 3rd party observer knows after the disclosure and what he can figure out


The display of the written problem in the video goes by pretty fast.  If you do not want to have to pause the video at that point, look at a photo of a paper copy of The Cheryl Problem

	http://smarturl.it/S-poreMathPblmPic


The video.  ~30 MB.

	http://smarturl.it/S-poreMathPblmVid


If you want a written explanation, try this blog entry from The New York Times

	https://bit.ly/1ynxxZk

In addition to its own explanation the blog entry has a link to an explanation from The Guardian.  If you do not like the explanation from The New York Times, try The Guardian.


There is post with an "official" explanation from the Singapore and Asian Schools Math Olympiad.  The same post also contains a photo.  The photo shows 2 pages from the test for the 2015 Asia International Mathematical Olympiad

	1) The cover page

	2) the page with Problem 23 and Problem 24

Problem 23 is covered up.  I think because students in other countries have not taken the test yet.  I am guessing that students in countries that have not given the test yet will do markedly better on Problem 24 than students in Singapore.  When they do, I will consider it absolute proof that Singapore is falling behind in math.  And that Singapore should radically change its math education system.  To the system in ... whatever country the smart kids live in.  Probably Asia.  Because Asia is a smart country.  Smart like people who think Asia is a country.

The "official" explanation of The Cheryl Problem

	http://smarturl.it/SAMSOMathPblmAns


This is the source of The Cheryl Problem as a meme. A Facebook post by Kenneth Kong, as corrected by Kong.  The original post was wrong about the grade level problem was intended for. To see the original post, click the link labelled 'Edited' in the corrected post.

	http://smarturl.it/S-poreMathPblmFB