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from the it-seemed-like-the-logical-thing-to-do-at-the-time dept.
A couple of months ago, it was a color-changing dress that blew out the neural circuits of the Internet. Now Kenneth Chang reports in the NYT that a problem from a math olympiad test for math-savvy high school-age students in Singapore is making the rounds on the internet that has perplexed puzzle problem solvers as they grapple with the simple question: "So when is Cheryl's birthday?"
Albert and Bernard just met Cheryl. “When’s your birthday?” Albert asked Cheryl.
Cheryl thought a second and said, “I’m not going to tell you, but I’ll give you some clues.” She wrote down a list of 10 dates:
May 15 — May 16 — May 19
June 17 — June 18
July 14 — July 16
August 14 — August 15 — August 17
“My birthday is one of these,” she said.
Then Cheryl whispered in Albert’s ear the month — and only the month — of her birthday. To Bernard, she whispered the day, and only the day.
“Can you figure it out now?” she asked Albert.
Albert: I don’t know when your birthday is, but I know Bernard doesn’t know, either.
Bernard: I didn’t know originally, but now I do.
Albert: Well, now I know, too!
When is Cheryl’s birthday?
Logical puzzles like this are common in Singapore. The Singapore math curriculum, which has a strong focus on logic-based problem solving, has been so successful that it's been adopted around the world. According to Terrance F. Ross, US students have made strides in math proficiency in recent years, but they still lag behind many of their peers internationally, falling at the middle of the pack in global rankings. In the same PISA report the U.S. placed 35th out of 64 countries in math. "And even though the "Cheryl's Birthday" question may be atypical of the average Singaporean classroom, perhaps it's still worth asking: Are you smarter than a (Singaporean) 10th-grader?"
(Score: 5, Insightful) by Tork on Thursday April 16 2015, @02:48AM
Indeed, your profession has to be fairly unique if you solve puzzles like this for living.
Maybe I do have an unusual profession, but I doubt it. I've had a number of jobs and even when I worked in retail there were times where deductive reasoning has been helpful. I think you summarized that really well right here:
This puzzle is not even a complicated one; all you need to do to solve it is to write down the dates and then emulate knowledge of both A and B, step by step. As you do that, you understand that there is only one solution that makes answers of A and B possible.
This sort of rationale applies to inventory, poor communication from a customer/client, reading a form that has poor handwriting on it, video analysis, interview at Google, etc. Sorry, I really don't get all the negativity with this one. Unless, of course, this isn't about the value of the puzzle at all and is instead just general begrudgery against anything mainstream.
🏳️🌈 Proud Ally 🏳️🌈
(Score: 2, Disagree) by tftp on Thursday April 16 2015, @03:03AM
Sorry, I really don't get all the negativity with this one. Unless, of course, this isn't about the value of the puzzle at all and is instead just general begrudgery against anything mainstream.
The puzzle is terribly contrived. People are reading crime stories where the plot is much thicker than that - and they enjoy those stories, as they are realistic. People can imagine themselves in the role of the detective. It all starts with a loosely defined problem. Then the protagonist tries to obtain more information - which appears to be contradictory, so someone is lying. He figures that out and gets one step closer to the solution.
The very first post here approaches the solution in a far more practical manner. We do not deal in riddles. Most people get angry when someone is toying with them. People want clear and specific information; they don't like to guess. It is not even practical to guess, as reliability of the solution becomes dependent on the fuzzy input. And, finally, not everyone is a mathematician. I recall an annoying mission in one of GTAs where you had to press various buttons on the controller to follow a dance tune. I am not capable of that. At some point I was thinking of connecting a GPIO to the controller and programming the button presses, as for the life of me I could not get through that mission. But eventually, after many tries, I just memorized enough of the pattern to pass.
(Score: 0) by Anonymous Coward on Thursday April 16 2015, @03:25AM
Manipulation is how people interact with each other. Don't like it when everyone is toying with you all the time? You are the problem, and we have an anger management class to fix you. If you don't learn to enjoy being lied to, you're fired.
(Score: 0) by Anonymous Coward on Thursday April 16 2015, @03:44AM
Not liking to be toyed with was itself a lie.
(Score: 0) by Anonymous Coward on Thursday April 16 2015, @10:56AM
I'm guessing you're not from Singapore, then.
If you think this story has *anything* to do with guesswork, then you're *really* not the intended audience for logic puzzles.
(Score: 0) by Anonymous Coward on Thursday April 16 2015, @02:19PM
It's guesswork because you have to make all sorts of assumptions to hopefully answer in the way they wanted you to answer. See a bunch of other replies on the assumptions you have to make.
(Score: 3, Funny) by tftp on Thursday April 16 2015, @05:21PM
It's actually worse than that. Your answer hinges on ALL OF THE RESPONDENTS correctly analyzing the problem and providing you with correct replies. This magnifies instability of the solution.
Imagine the following exchange at work:
Boss: Listen, John. We have a customer who is willing to pay us $50M for a job. I need you to figure out how much that job will cost us, so we can bid or no bid on it.
John: OK, boss, I'm on it.
John: Hey, Jane, how much this will cost us?
Jane: John, it will be between ten and a hundred million, but it's an even number. Ask Jill for more.
Jill: John, it will be not a prime number. Ask Will for more.
Will: John, if you square this number and then calculate a factorial, it will end in two. Ask James for more.
. . . . . .
Boss: So, John, what is it? I'd hate to lose our shirt on this contract if we make a mistake.
John: Boss, I talked to five hundred and thirty seven people in our company. None of them gave me a specific answer. All I have is a bunch of vague hints. I summarized them in this here spreadsheet. According to my calculations, if I am correct, the answer would be 37 million, and we will make a reasonable profit on it. However three hundred and eighty two answers are the keystone of this solution - if they are wrong then our costs could be anywhere from one million to three hundred million. I hope, boss, that this answers your question.
Boss: @%$#!!!
(Score: 1, Interesting) by Anonymous Coward on Thursday April 16 2015, @08:20AM
This sort of rationale applies to ... poor communication from a customer/client
No it doesn't. In too many cases you cannot use this sort of logic when you get poor communication from a customer/client.
That's because lots of customers and clients do not think clearly and logically. So they might send you some garbage of an email.
Trying to use logic on the garbage they send you often leads to wrong conclusions (GIGO).
So when you detect some ambiguity what you have to do is work out a way to get them to send something hopefully clearer. Sometimes it's simple as just asking, at other times you need some "people sensitive" way of doing it.
Just going "But you said this in your original email and so we'll hold you to that otherwise see our lawyers" might be fine if you only want to do one job with that sort of customer (and they are rather common- after all in many cases the clear thinking ones might not need you as much as those with candy floss for brains).
(Score: 2) by Tork on Thursday April 16 2015, @03:47PM
No it doesn't. In too many cases you cannot use this sort of logic when you get poor communication from a customer/client.
And how exactly would you determine if you do not have enough information from them? ;)
🏳️🌈 Proud Ally 🏳️🌈
(Score: 1) by tftp on Thursday April 16 2015, @11:23PM
And how exactly would you determine if you do not have enough information from them? ;)
You determine that by talking to them and figuring out if they understand what they are asking you to do. Plenty of customers have unrealistic expectations. It would be a disaster to start a job only to shock the customer in the end. You always want to ensure that the customer knows how much is he going to pay and what is he going to get - before you even start. The customer may be silly and illogical, but that won't prevent him from suing you. You cannot depend on hints - you always want everything important clearly spelled out and clearly understood by all parties.
(Score: 2) by Tork on Thursday April 16 2015, @11:59PM
🏳️🌈 Proud Ally 🏳️🌈
(Score: 1) by tftp on Friday April 17 2015, @12:17AM
I'm saying that most communication is poor, and you try to make at least the essential communication - that can make or break your business - as clear and obvious as possible. It may well be that you will be listening to your contract being read aloud, in court. You want to make sure that you made all the effort that you could to deliver your message, and that it's not your fault that the other guy still managed to misinterpret it.
Obviously, if the contract contains confusing messages that need to be read by three lawyers and five mathematicians from Singapore, this won't fly real well in court even if they are mathematically correct, like this riddle. Can you imagine that the girl would be giving answers like that to two police officers? Or that they will even attempt to figure out the answer?
(Score: 2) by DeathMonkey on Thursday April 16 2015, @06:06PM
This puzzle is not even a complicated one; all you need to do to solve it is to write down the dates and then emulate knowledge of both A and B, step by step. As you do that, you understand that there is only one solution that makes answers of A and B possible.
Basically, process of elimination.
I'm sure nobody on this website has used the process of elimination while troubleshooting something.
How to mill this piece without incurring too much vibration and tool wear? How to design this amplifier so that it won't oscillate?
No troubleshooting to be seen here, move along.