snopes.com  

Go Back   snopes.com > SLC Central > Social Studies

Reply
 
Thread Tools Display Modes
  #1  
Old 15 April 2015, 12:25 AM
Andrew of Ware's Avatar
Andrew of Ware Andrew of Ware is offline
 
Join Date: 22 April 2003
Location: Ware, Hertfordshire, England
Posts: 8,017
Teacher Cheryl's Birthday: Singapore's maths puzzle baffles world

A school maths question posted on Facebook by a Singaporean TV presenter has stumped thousands, and left many asking if that's really what is expected of Singaporean students.

http://www.bbc.co.uk/news/world-asia-32297367

Social media initially reported that the problem was for children aged 11, but it turned out to be for the top 40% of children aged 15. I would try and solve it now, but it is 25 past midnight and I really must get to bed. When I get up tomorrow I hope that you have solved it - without looking at the video with the solution!
Reply With Quote
  #2  
Old 15 April 2015, 12:54 AM
crocoduck_hunter's Avatar
crocoduck_hunter crocoduck_hunter is offline
 
Join Date: 27 May 2009
Location: Roseburg, OR
Posts: 13,067
Default

I always hated these types of problems. But it seems like less of a math problem and more of a logic problem.

Or a pun that didn't translate well into English.
Reply With Quote
  #3  
Old 15 April 2015, 01:34 AM
Tootsie Plunkette's Avatar
Tootsie Plunkette Tootsie Plunkette is offline
 
Join Date: 26 October 2001
Location: Seattle, WA
Posts: 10,129
Ponder

I puzzled over that one yesterday on my bus ride home. I actually got the correct answer, which surprised the heck out of me!
Reply With Quote
  #4  
Old 15 April 2015, 02:28 AM
Jahungo's Avatar
Jahungo Jahungo is offline
 
Join Date: 23 May 2007
Location: New York, NY
Posts: 5,351
Default

It's a tricky prompt, but if you are used to dealing with this sort of question and have been practicing applying logical approaches to word problems, it should not be that difficult.

It simply requires going through each step of new information in turn and ruling out choices that are inconsistent with that new information. How to do that isn't immediately obvious if you're not used to it (it took me a few false starts in my thinking), but (hopefully) these kids have been learning and practicing the approaches to solve these types of problems!
Reply With Quote
  #5  
Old 15 April 2015, 02:31 AM
Jahungo's Avatar
Jahungo Jahungo is offline
 
Join Date: 23 May 2007
Location: New York, NY
Posts: 5,351
Default

To me it is rather interesting that in Singapore they not only have tests in English, but also use European names in their prompts.
Reply With Quote
  #6  
Old 15 April 2015, 02:47 AM
ganzfeld's Avatar
ganzfeld ganzfeld is offline
 
Join Date: 05 September 2005
Location: Kyoto, Japan
Posts: 23,760
Icon05

What language did you expect their tests to be in? English is the language of Singapore. (It has a few other official languages but English is the language of most education, etc.)
Reply With Quote
  #7  
Old 15 April 2015, 02:55 AM
Errata's Avatar
Errata Errata is offline
 
Join Date: 02 August 2005
Location: Santa Barbara, CA
Posts: 13,189
Default

Quote:
Originally Posted by Jahungo View Post
It's a tricky prompt, but if you are used to dealing with this sort of question and have been practicing applying logical approaches to word problems, it should not be that difficult.
Yes, I found it pretty simple. Given the buildup, I was concerned that it was some sort of trick question, but no.

It's impossible to say for sure, but I'm pretty confident that it wouldn't have been much more difficult when I was 11.

Last edited by Errata; 15 April 2015 at 03:05 AM.
Reply With Quote
  #8  
Old 15 April 2015, 03:53 AM
ganzfeld's Avatar
ganzfeld ganzfeld is offline
 
Join Date: 05 September 2005
Location: Kyoto, Japan
Posts: 23,760
Default

That is a fun problem, though. I wish we'd had more problems like that in school.

I meant to mention about the names in the question, replying to Jahungo: The majority of given names in Singapore are typically western names. So it's not as if the children would be looking at foreign-sounding names. Almost all of their classmates would have names similar to the ones in the problem.
Reply With Quote
  #9  
Old 15 April 2015, 04:23 AM
Errata's Avatar
Errata Errata is offline
 
Join Date: 02 August 2005
Location: Santa Barbara, CA
Posts: 13,189
Default

Agreed. Some of our math teachers would have challenging problems like that that nerds could do for fun, and regional math competitions would occasionally have logic problems. But the curriculum itself was much more mundane.

Looking for this sort of challenge is part of the reason I got into programming as a kid. Every algorithm is a logic puzzle.
Reply With Quote
  #10  
Old 15 April 2015, 04:47 AM
erwins's Avatar
erwins erwins is offline
 
Join Date: 04 April 2006
Location: Portland, OR
Posts: 12,331
Default

A third of the LSAT was analytical problems like this when I took it. I sometimes like puzzling through them, but a whole bunch of them in a row on a timed, career-critical test was a bit brutal.
Reply With Quote
  #11  
Old 15 April 2015, 02:34 PM
UEL's Avatar
UEL UEL is offline
 
Join Date: 01 August 2004
Location: Fredericton, Canada
Posts: 9,367
Baseball

Well, I got it wrong.

I had an answer that I thought met all the requirements, but was not comfortable with.

Then, I saw the answer and I knew I was out to lunch.

After seeing the reveal, I understand how they got it, and if it had possibly been worded in just another subtle way (change doesn't for can't) in the first statement, I would have solved it.

Very interesting puzzle.
Reply With Quote
  #12  
Old 15 April 2015, 03:55 PM
she-geek's Avatar
she-geek she-geek is offline
 
Join Date: 12 April 2009
Location: Rochester, MN
Posts: 588
Default

See, I'm at the "Why wouldn't Cheryl just TELL them?" stage.
Reply With Quote
  #13  
Old 15 April 2015, 04:17 PM
chillas's Avatar
chillas chillas is offline
 
Join Date: 09 September 2002
Location: Columbus, OH
Posts: 11,832
Default

That was a good one. Took me some thinking but I came up with the correct answer. I always enjoyed well constructed logic puzzles.
Reply With Quote
  #14  
Old 15 April 2015, 04:49 PM
crocoduck_hunter's Avatar
crocoduck_hunter crocoduck_hunter is offline
 
Join Date: 27 May 2009
Location: Roseburg, OR
Posts: 13,067
Default

Quote:
Originally Posted by she-geek View Post
See, I'm at the "Why wouldn't Cheryl just TELL them?" stage.
Yeah, me too.
Reply With Quote
  #15  
Old 15 April 2015, 04:56 PM
GenYus234's Avatar
GenYus234 GenYus234 is online now
 
Join Date: 02 August 2005
Location: Mesa, AZ
Posts: 26,570
Default

Quote:
Originally Posted by she-geek View Post
See, I'm at the "Why wouldn't Cheryl just TELL them?" stage.
Or why Albert can't tell Bernard, "It is in July." and Bernard can't tell Albert, "It is the 16th."
Reply With Quote
  #16  
Old 15 April 2015, 05:06 PM
Richard W's Avatar
Richard W Richard W is offline
 
Join Date: 19 February 2000
Location: High Wycombe, UK
Posts: 26,406
Default

I hadn't realised until I read this article that it's gone viral partly because there are two possible answers, depending on how you interpret the question:

http://www.theguardian.com/science/a...n-of-thatdress

I read it, got the answer (which turns out to be the "wrong" one) and thought no more of it - I didn't bother to check my answer as I was confident in my reasoning. So it wasn't until I saw the article above that I realised the ambiguity.

Basically, the question doesn't say how Albert knows that Bernard doesn't know the answer. If you assume (as I did) that he was given that information (as we were) before the conversation above - he states it as axiomatic - you get one answer. If you assume that he had to work out that Bernard didn't know the answer, then you get a different answer.

I suppose since the question doesn't say that anybody told Albert, then the answer where he has to work out that Bernard doesn't know is "more correct", because the other one includes an assumption that's not actually stated anywhere in the question - such as that Albert knew Bernard didn't know because neither of them had said "I know the date", for example. But it's still a bad exam question because of that ambiguity, I'd say.

The article goes through the "wrong" reasoning because it isn't the answer that the writer got, but it doesn't go through the "right" reasoning, so you can still read it if you want to work out the answer for yourself.

It's still nothing to do with the dress picture, though... it's more like those questions with a string of operators that are ambiguous because the rules of operator precedence aren't as clear and universal as people think. Those are bad because no real mathematician (or anybody trying to communicate clearly) would deliberately express something in a way that was intentionally ambiguous and then criticise you for getting it wrong. This question is unintentionally ambiguous, but any disagreement is still in the ambiguity rather than the logic.

I like this joke from the article above:

Quote:
Three logicians walk into a bar. The barman asks “does everyone want a drink?” The first logician says, “I don’t know”. The second logician says, “I don’t know”. The third logician says, “Yes”.
Reply With Quote
  #17  
Old 15 April 2015, 05:32 PM
Errata's Avatar
Errata Errata is offline
 
Join Date: 02 August 2005
Location: Santa Barbara, CA
Posts: 13,189
Default

Quote:
Originally Posted by Richard W View Post
I hadn't realised until I read this article that it's gone viral partly because there are two possible answers, depending on how you interpret the question:

http://www.theguardian.com/science/a...n-of-thatdress
That doesn't make any sense. If they don't know the problem statement, they don't know enough to be making any of these deductions.

Quote:
4. Bernard realises what Albert has realised, which is that Bernard does not have 18 or 19. Now if Albert was holding June he would know the answer, because there is only one remaining date in June, namely June 17. So Bernard deduces it is not June.
Why would Bernard know that Albert has a month if the whole basis of your flawed analysis is that they don't know how the problem works? He couldn't deduce that Albert knows a month based on what he's said so far.

If Cheryl is giving out secret additional information that is not listed in the problem statement, as this analysis assumes ("Maybe Cheryl told him as much"), then we can imagine all sorts of hypothetical things that she might have said that aren't listed in the problem, and any semblance of logic goes out the window. This interpretation requires making a whole series of unsupported assumptions. When you start viewing the problem that way, there are all sorts of answers you might come up with, and no way to distinguish between them.

In any of these problems, they don't have a 10 page long problem description that rules out any possible misinterpretations. Part of the problem is you have to interpret as a reasonable person would do and not go off on some weird tangent that does not lead to an internally consistent problem statement. People who are picking these sorts of nits miss the point. If you try to understand what they're trying to say in the way that makes the most sense, it is generally unambiguous what that is.

Last edited by Errata; 15 April 2015 at 05:38 PM.
Reply With Quote
  #18  
Old 15 April 2015, 06:50 PM
pinqy pinqy is offline
 
Join Date: 20 February 2000
Location: Northern Virginia
Posts: 11,647
Default

Quote:
Originally Posted by Richard W View Post
Basically, the question doesn't say how Albert knows that Bernard doesn't know the answer. If you assume (as I did) that he was given that information (as we were) before the conversation above - he states it as axiomatic - you get one answer. If you assume that he had to work out that Bernard didn't know the answer, then you get a different answer.
I'm not understanding. We know that Albert was only told the month. We know that Bernard was only told the day. We can assume that each knows this as well.

Quote:
I suppose since the question doesn't say that anybody told Albert, then the answer where he has to work out that Bernard doesn't know is "more correct", because the other one includes an assumption that's not actually stated anywhere in the question - such as that Albert knew Bernard didn't know because neither of them had said "I know the date", for example. But it's still a bad exam question because of that ambiguity, I'd say.
I'm not getting the ambiguity, or why anyone would assume that Albert knew Bernard didn't know by any other means than logic.

[qutoe]The article goes through the "wrong" reasoning because it isn't the answer that the writer got, but it doesn't go through the "right" reasoning, so you can still read it if you want to work out the answer for yourself.
[/quote]

Let's walk through.
If Albert had the month of May, he could not know if Bernard knew the date or not because Bernard might have 19 as the day.
If Albert had June, same thing, except for the 18th.
Therefore, the only way Albert could know that Bernard did not know the date would be if the month were July or August.

Bernard, being a perfect logician, know knows this. And because he now knows the month is July or August, he now knows the date. If the day Bernard knew was the 14th, then he wouldn't know the month. Since he does know the month, then the day must be 15, 16, or 17....the days unique to either July or August.

Albert, also a perfect logician, would know all this. And he now knows the date. If the month were August, then Albert could not know if the day was the 15th or 17th. The only way he could know the date would be if the month was July and the only possibility was the 16th.

Quote:
This question is unintentionally ambiguous, but any disagreement is still in the ambiguity rather than the logic
But it's not ambiguous. The only way to get August 17th is if you assume a fact that's not given. That's a bad assumption and there is no reason to make it.
Reply With Quote
  #19  
Old 15 April 2015, 07:17 PM
Dr. Dave Dr. Dave is offline
 
Join Date: 28 June 2005
Location: Montgomery County, MD
Posts: 5,279
Default

I agree with the guys that say that there is no ambiguity. In any logic problem game, there are no outside assumptions.

Maybe Cheryl told Albert that Bernard does not know? The whole idea is that the piece of info that Albert gets- namely the month- gives him enough information to deduce that Bernard does not know from his piece of information- namely the day.

If you make other assumptions, then you can assume anything. Maybe he looked in her wallet!

At least the "ask the building superintendent and give him the altimeter as a thank you gift" is clever and funny.
Reply With Quote
  #20  
Old 15 April 2015, 07:30 PM
GenYus234's Avatar
GenYus234 GenYus234 is online now
 
Join Date: 02 August 2005
Location: Mesa, AZ
Posts: 26,570
Default

I prefer "drop the altimeter off the roof and time how long until it hits the ground" myself.

For me, the use of "Bernand can't know" would make the confusion go away.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mystery Mars haze baffles scientists TallGeekyGirl Techno-Babble 0 17 February 2015 07:07 PM
Batman bin Suparman jailed in Singapore E. Q. Taft Police Blotter 0 13 November 2013 04:10 AM
Worst-Ever Right Whale Die-Off Continues to Puzzle A Turtle Named Mack Wild Kingdom 0 10 May 2013 06:10 PM
'Fishing under the ice' viral video baffles viewers snopes Fauxtography 6 06 January 2012 01:20 AM
German company claims puzzle is world's biggest snopes Trivia 6 01 October 2008 09:28 PM


All times are GMT. The time now is 10:31 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.