Singapore Maths' Puzzle

Post by **OpiateOfTheMasses** » Tue Apr 14, 2015 10:09 pm

I have a new found respect for kids that go to school in Singapore:

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

I think this is actually relatively hard for 15 year olds. In fact I showed it round the guys (and gals!) at work today and most of them didn't even know how to solve it let alone come up with the right answer...

So... without scrolling down the page and seeing the answer - how many of you can figure it out?

phe_de · Post by **phe_de** » Tue Apr 14, 2015 10:26 pm

Fck problems that are not written in mathematic language...

The way it is phrased I can't figure out what Cheryl tells Albert and Bernard.
"Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively."

This means, in English language as taught in Germany: Cheryl tells each of them the month and day of her birthday. Which would mean that they both know it.
But this can't be true, otherwise it would not be a logic problem.

Without spoiling the answer, could the statement be rephrased as follows:
"Cheryl tells Albert the month of her birthday, and Bernard the day of her birthday. Albert knows that Cheryl told Bernard the day, and Bernard knows that Cheryl told Albert the month of her birthday."

In that case, I come up with three possible answers. So I probably understood it wrong.

EDIT: I just looked at it again. If my interpretation is correct, then we can come with one answer. July 16
EDIT again: I was right.

Post by **OpiateOfTheMasses** » Tue Apr 14, 2015 10:30 pm

Yes Albert knows the Month and Bernard knows the Day. It doesn't say that they each know that the other has been told the month or day but I've assumed that they do know this.

(And I share your pain on questions that are written out in sentences rather than mathematical language - they're often more difficult to understand than the problem! But the idea is to make it "easier" for the kids...)

Ptolemy_Banana · Post by **Ptolemy_Banana** » Wed Apr 15, 2015 8:20 am

phe_de wrote:Fck problems that are not written in mathematic language...

The way it is phrased I can't figure out what Cheryl tells Albert and Bernard.
"Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively."

This means, in English language as taught in Germany: Cheryl tells each of them the month and day of her birthday. Which would mean that they both know it.

The word 'respectively' at the end of the of the sentence indicates that the first person is told the first detail, the second person the second details etc.

Ptolemy_Banana · Post by **Ptolemy_Banana** » Wed Apr 15, 2015 8:25 am

OpiateOfTheMasses wrote:I have a new found respect for kids that go to school in Singapore:

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

I think this is actually relatively hard for 15 year olds. In fact I showed it round the guys (and gals!) at work today and most of them didn't even know how to solve it let alone come up with the right answer...

So... without scrolling down the page and seeing the answer - how many of you can figure it out?

I think people are impressed by this because it's unlike what they were used to. The answer is achieved by a process of elimination and the real difficulty is in interpreting exactly what you are told. I'd imagine children who are regularly set puzzles like this wouldn't find it particularly difficult.

BruceSmith78 · Post by **BruceSmith78** » Wed Apr 15, 2015 1:45 pm

I figured out what they want the right answer to be, and then watched the explanation to see if they explained what was bothering me, but they didn't. So, spoilers.

I knew we could eliminate May and June based on Bernard's initial statement, since they both had a unique day and Albert said Bernard couldn't know the date, but then when Bernard said he knows the date now, all we know is it could be one of three days. It can't be the 14th since that day is in both July's options and August's options, and so the only way Albert could know it is if he goes with the month with only one other option, but how did he know it wasn't in August? He knew that he had narrowed it down to August and July for Bernard, and he knew it couldn't be the 14th since that's in both months, but after that he's SOL. It could be any of the remaining three dates.

Basically, Albert is a mind reader, not a logician, which throws the whole problem out the window.

*edit* I thought about it more, and it hit me. Albert already knew the month, duh. It makes sense now, and I feel stupid.

phe_de · Post by **phe_de** » Wed Apr 15, 2015 6:30 pm

BruceSmith78 wrote:It could be any of the remaining three dates.

Basically, Albert is a mind reader, not a logician, which throws the whole problem out the window.

That's exactly where I was stuck after the first thinking. But then I got the last clue.

And one reason why I could solve it so quickly is that decades ago, when I was 15 or 16 years old and still at school, I had encountered a problem that resembles it. I'll tell it the way I remember it; it's probably not politically correct anymore.

5 mathematicians get captured by a tribe of cannibals.
Each of them are put in a separate cauldron. There are 2 green and 3 red cauldrons. The mathematicians can not see what cauldron they are put in, but they know that there are 2 green and 3 red cauldrons, and none of the mathematicians is colorblind.
They are put the following way:
2 mathematicians, then a tree, then the remaining three mathematicians.

M1 M2 T M3 M4 M5

They can only face right.
M1 sees the cauldron of M2 and the tree.
M2 sees the tree.
M3 sees the cauldrons of M4 and M5.
M4 sees the cauldron of M5.
M5 sees nothing.

The chief of the cannibals then says: If one of you can guess the colour of the cauldron he is in, I'll let you go.
He then asks the mathematicians from M1 to M5. All mathematicians can hear the answers.

M1 says: I don't know.
M2 says: I don't know.
M3 says: I don't know.
M4 says: I don't know.
M5 says: I know!

And M5 is right.
What is the colour of the cauldron M5 is in?

At the time, it was asked in a classroom; and the class discussed for about 15 minutes, before coming to the right conclusion.
The answer is: red.

sikax · Post by **sikax** » Wed Apr 15, 2015 6:57 pm

"Slight sexual dynamic"

Gypsy-Vanner · Post by **Gypsy-Vanner** » Wed Apr 15, 2015 8:37 pm

So, I tried to understand based on the explanation and I have finally come to the conclusion that this kind of crap can go fuck a donkey.

Post by **OpiateOfTheMasses** » Wed Apr 15, 2015 8:58 pm

Gypsy-Vanner wrote:So, I tried to understand based on the explanation and I have finally come to the conclusion that this kind of crap can go fuck a donkey.

Funnily enough my missus had a surprisingly similar reaction to this when I showed it to her and subsequently tried to explain it to her!

CashRules · Post by **CashRules** » Wed Apr 15, 2015 9:02 pm

It would be easy to solve if it had been worded correctly. As written it's just a jumbled mess of barely comprehensible nonsense disguised as a logic puzzle.

Dr_Liszt · Post by **Dr_Liszt** » Wed Apr 15, 2015 9:08 pm

The obvious answer to this one is kill Cheryl for not giving straightforward answers.

I guessed May 19. Don't care if I'm correct.

CashRules · Post by **CashRules** » Wed Apr 15, 2015 9:09 pm

Has anybody actually named their kid Cheryl in the past 40 years?

Post by **OpiateOfTheMasses** » Wed Apr 15, 2015 9:19 pm

Maybe the name's really popular in Singapore? [shrug]

Ptolemy_Banana · Post by **Ptolemy_Banana** » Thu Apr 16, 2015 12:24 am

CashRules wrote:Has anybody actually named their kid Cheryl in the past 40 years?

I think the last man named Albert had a piercing named after him.

Anakin McFly · Post by **Anakin McFly** » Thu Apr 16, 2015 1:16 am

I'm still amused that this actually made world news.

A local commenter said, "Just who is Cheryl and why does she have such a hold over young men?"

I got Aug 17 initially, because I made that mistake of thinking that Bernard had told Albert that he didn't know the date.

CashRules · Post by **CashRules** » Thu Apr 16, 2015 3:11 am

If it was actually worded correctly it's so easy that it's safe to say that anyone who doesn't get the answer within fifteen seconds is somebody who should probably be exterminated.

BruceSmith78 · Post by **BruceSmith78** » Thu Apr 16, 2015 3:40 am

phe_de wrote:
BruceSmith78 wrote:It could be any of the remaining three dates.

Basically, Albert is a mind reader, not a logician, which throws the whole problem out the window.
That's exactly where I was stuck after the first thinking. But then I got the last clue.

And one reason why I could solve it so quickly is that decades ago, when I was 15 or 16 years old and still at school, I had encountered a problem that resembles it. I'll tell it the way I remember it; it's probably not politically correct anymore.

5 mathematicians get captured by a tribe of cannibals.
Each of them are put in a separate cauldron. There are 2 green and 3 red cauldrons. The mathematicians can not see what cauldron they are put in, but they know that there are 2 green and 3 red cauldrons, and none of the mathematicians is colorblind.
They are put the following way:
2 mathematicians, then a tree, then the remaining three mathematicians.

M1 M2 T M3 M4 M5

They can only face right.
M1 sees the cauldron of M2 and the tree.
M2 sees the tree.
M3 sees the cauldrons of M4 and M5.
M4 sees the cauldron of M5.
M5 sees nothing.

The chief of the cannibals then says: If one of you can guess the colour of the cauldron he is in, I'll let you go.
He then asks the mathematicians from M1 to M5. All mathematicians can hear the answers.

M1 says: I don't know.
M2 says: I don't know.
M3 says: I don't know.
M4 says: I don't know.
M5 says: I know!

And M5 is right.
What is the colour of the cauldron M5 is in?

At the time, it was asked in a classroom; and the class discussed for about 15 minutes, before coming to the right conclusion.
The answer is: red.

Clearly the first four are idiots. They're allowed to guess and all they say is, "I don't know"? If I was first I'd fucking say red, cuz you got a 75% chance of being right if the cauldron next to you is green and a 50% chance of being right if it's red. And if I was second my guess would depend on the previous guy's guess, and whether or not he was right, etc. I sure as fuck wouldn't say "I don't know." Some logicians.

I get the answer though. The first two are red herrings. The third guy would know he's in a red cauldron if the last two were green, so they're either both red or one's red and one's green. The 4th guy would know he's in a red cauldron if the last one was green, but since he doesn't know that means the last isn't green, it's red.

Monk · Post by **Monk** » Thu Apr 16, 2015 5:41 pm

Gypsy-Vanner wrote:So, I tried to understand based on the explanation and I have finally come to the conclusion that this kind of crap can go fuck a donkey.

I found it difficult but managed to figure it out. What's tricky is that you have to constantly think from the perspective of each person. To understand, try working backwards. The date is July 16th. This means that:

-Albert knows the month is July
-Bernard knows that the day is 16

-Because the month is July, Albert knows that Bernard cannot know. The only way Bernard would know the month is if the day he was given was either 18 or 19 (there is only one month for each day, June and May respectively). Since July does not have either 18 or 19, Albert knows that Bernard cannot know the month.

-If Albert claims that he knows Bernard cannot know, then Bernard now knows that the month must be either July or August based on the same reasoning as above. Albert could only know that Bernard doesn't know if the month did not include the days 18 or 19.

-Since Bernard knows the day is 16, he knows that the date is July 16th. This is because there is no August 16th option.

-Albert knows that month is July. Bernard was able to figure out the date. Albert can rule out July 14th, because both August and July have the 14th - Bernard wouldn't know if it was August or July if the day was 14. This only leaves July 16th, so now Albert knows too.

Does that make sense?

Gypsy-Vanner · Post by **Gypsy-Vanner** » Thu Apr 16, 2015 6:56 pm

I stopped at the word "tricky" because I was thinking it would have been cooler if you had used "tricksey" instead.

Monk · Post by **Monk** » Thu Apr 16, 2015 8:11 pm

Gypsy-Vanner · Post by **Gypsy-Vanner** » Thu Apr 16, 2015 9:18 pm

It's ok, I appreciate the effort. I'm just really terrible with math beyond simple functions.

CashRules · Post by **CashRules** » Thu Apr 16, 2015 9:19 pm

Gypsy-Vanner wrote:It's ok, I appreciate the effort. I'm just really terrible with math beyond simple functions.

We already knew you're a woman.

Post by **aels** » Thu Apr 16, 2015 9:26 pm

CashRules · Post by **CashRules** » Thu Apr 16, 2015 9:30 pm

^bringing sexy back.

Post by **aels** » Thu Apr 16, 2015 9:32 pm

God, I hope you meant me and not that cat.

CashRules · Post by **CashRules** » Thu Apr 16, 2015 9:33 pm

That cat is cool.

Post by **OpiateOfTheMasses** » Thu Apr 16, 2015 9:56 pm

There generally seems to be a male-female divide here on this.

C'mon! Let's not conform to stereotypes! Lets have more maths chicks (remember - maths is sexy!) and more guys that can't add up please...

Whitey · Post by **Whitey** » Thu Apr 16, 2015 10:01 pm

I'm upset that neither of you have managed to make THE obvious rude joke about that picture.

Post by **aels** » Thu Apr 16, 2015 10:03 pm

Whitey wrote:I'm upset that neither of you have managed to make THE obvious rude joke about that picture.

Dripping wet pussy?

Post by **aels** » Thu Apr 16, 2015 10:04 pm

OpiateOfTheMasses wrote:There generally seems to be a male-female divide here on this.

C'mon! Let's not conform to stereotypes! Lets have more maths chicks (remember - maths is sexy!) and more guys that can't add up please...

I'm okay at maths. I was top five at my school. I don't like it and complicated maths makes me frightened and confused - I don't have a mathsy brain in the same way that I don't have a spatial brain - but I'm pretty good at basic shit. And algebra, I was rad at algebra.

Whitey · Post by **Whitey** » Thu Apr 16, 2015 10:05 pm

aels wrote:
Whitey wrote:I'm upset that neither of you have managed to make THE obvious rude joke about that picture.
Dripping wet pussy?

Quite so. Don't let me catch you being appropriate on this board again.

Dr_Liszt · Post by **Dr_Liszt** » Thu Apr 16, 2015 11:47 pm

OpiateOfTheMasses wrote:There generally seems to be a male-female divide here on this.

C'mon! Let's not conform to stereotypes! Lets have more maths chicks (remember - maths is sexy!) and more guys that can't add up please...

That's not math! That's "I'm going to scramble a lot of words to confuse you and laugh at your incompetence."

Post by **Gendo** » Fri Apr 17, 2015 11:36 pm

OpiateOfTheMasses wrote:There generally seems to be a male-female divide here on this.

C'mon! Let's not conform to stereotypes! Lets have more maths chicks (remember - maths is sexy!) and more guys that can't add up please...

Fine. I got the answer wrong when I first looked at it. Should have thought more carefully.

Monk · Post by **Monk** » Sat Apr 18, 2015 11:59 am

aels wrote:
OpiateOfTheMasses wrote:There generally seems to be a male-female divide here on this.

C'mon! Let's not conform to stereotypes! Lets have more maths chicks (remember - maths is sexy!) and more guys that can't add up please...
I'm okay at maths. I was top five at my school. I don't like it and complicated maths makes me frightened and confused - I don't have a mathsy brain in the same way that I don't have a spatial brain - but I'm pretty good at basic shit. And algebra, I was rad at algebra.

I'm actually not that great either. I think the problem is that math should be viewed like any other skill - for the majority of people, it requires practice.

BruceSmith78 · Post by **BruceSmith78** » Sat Apr 18, 2015 12:43 pm

I agree with Dork. This isn't math. I didn't use any equations or anything, I just thought about the possibilities.

Blade Azaezel · Post by **Blade Azaezel** » Sat Apr 18, 2015 1:34 pm

Yeah, you can't say something is a maths puzzle just because there are numbers in it

Post by **Gendo** » Mon Apr 20, 2015 3:10 pm

It's a logic puzzle; which is different but similar to a math puzzle.

Pope Bucky · Post by **Pope Bucky** » Mon Apr 20, 2015 3:15 pm

This is definitely a logic puzzle. It could just as easily have been shapes and colors.

IIRC, all my logic courses in college were in the philosophy department.

phe_de · Post by **phe_de** » Mon Apr 20, 2015 3:42 pm

Pope Bucky wrote:This is definitely a logic puzzle. It could just as easily have been shapes and colors.

True. Just like with Sudoku.
Where I live people often assume that being good at maths helps with Sudoku. Just because there are numbers in it.

Real maths puzzles are "KenDoku" and "The Good Count" (Android apps). There you need to calculate in order to solve them.

Post by **Gendo** » Mon Apr 20, 2015 4:05 pm

Well I think that being good at math helps with Sudoku in an indirect way... pretty sure people who are good at math will tend to be more likely to be good at logic, and vice-versa.

Kendoku is both math and logic... while there is math involved; it's very basic arithmetic that doesn't require being all that good with math. It still requires the same sort of logic as sudoku.

Monk · Post by **Monk** » Mon Apr 20, 2015 5:32 pm

BruceSmith78 wrote:I agree with Dork. This isn't math. I didn't use any equations or anything, I just thought about the possibilities.

Er...which one is Dork?

Post by **Gendo** » Mon Apr 20, 2015 5:44 pm

Monk wrote:
BruceSmith78 wrote:I agree with Dork. This isn't math. I didn't use any equations or anything, I just thought about the possibilities.

Er...which one is Dork?

"I agree with Dork" is just a meme meaning "I agree".

Dr_Liszt · Post by **Dr_Liszt** » Mon Apr 20, 2015 6:20 pm

I am dork.

it's about time you guys figured it out.

Post by **OpiateOfTheMasses** » Mon Apr 20, 2015 9:34 pm

phe_de wrote:
Pope Bucky wrote:This is definitely a logic puzzle. It could just as easily have been shapes and colors.
True. Just like with Sudoku.
Where I live people often assume that being good at maths helps with Sudoku. Just because there are numbers in it.

Real maths puzzles are "KenDoku" and "The Good Count" (Android apps). There you need to calculate in order to solve them.

Most of the maths I remember doing didn't have many numbers in it and I didn't have any use for a calculator when I was solving it...

So whilst I take your point, I would counter with Maths is largely logic - not numbers - there's a hell of a lot more to it than just arithmetic!

CashRules · Post by **CashRules** » Mon Apr 20, 2015 10:19 pm

Monk, you may have been gone from the IMDB board at the time, but the "I agree with Dork" meme started when GI made a reply to one of Dork's threads stating "I agree with Dork" and then listed the things he "agreed" with Dork about, all of which were the exact opposite of what Dork had said. So, being me, I followed that up by stating "I agree with Dork, gun ownership should be mandatory and women shouldn't vote because it's their husbands place to vote on their behalf." Fun times.

Dr_Liszt · Post by **Dr_Liszt** » Mon Apr 20, 2015 10:32 pm

I miss good ol' Pete. We should invite him here.

CashRules · Post by **CashRules** » Mon Apr 20, 2015 10:38 pm

You should shut your face, woman.

Post by **Islandmur** » Mon Apr 20, 2015 10:58 pm

I just treated it like a sudoku puzzle.

Post by **Gendo** » Tue Apr 21, 2015 6:07 am

Dr_Liszt wrote:I miss good ol' Pete. We should invite him here.

I did actually. He never responded to my PM.