Posted on 04/16/2015 9:29:47 AM PDT by QT3.14
One word problem from a Singaporean school exam briefly became the talk of the Internet last weekend....[Snip]... The puzzle went viral across the country, with people ranging from perplexed adults to eager teenagers grappling with the simple question: "So when is Cheryl's birthday?"
(Excerpt) Read more at theatlantic.com ...
Ugh. No. I’m wrong.
Bernard would know if Bernard had been told 18 or 19. Those only have 2 possibilities.
So Albert knows that Bernard does not know, because Albert had been told something other than May or June (i.e. July or August).
Once Bernard knows that July or August are the only possibilities, then any of 15, 16, or 17 would imply an exact date. So how can Albert’s knowledge advance from there, I am unsure. It seems like they are trying to imply that it is July 16, but more conversation would have to transpire.
Albert and Bernard each have been given correct data.
Albert was given the month but, as there are multiple possibilities within each month, he can not determine the date.
Bernard was given the day. Possible days are: 14, 15, 16, 17, 18, and 19. Except for 18 and 19 there are multiple occurrances of each day.
Albert announces that he knows that Bernard can not know the date. This tells Bernard that the day is not unique. Therefore May 19 and June 18 can be ruled out.
There is now only one month with a single possible day: June. Therefore June 17
No, the day has to be unique like 18 or 19, so the person being told the day knows the date straight out. Then only the person with the month has to solve the problem.
2 variables with 1 unknown is solvable. 2 variables with 2 unknowns cant be solved. If say the date is the 19th and the other is told May, then their are 2 unknowns since the guy with the month has 3 to choose from.
With June 18, the guy with the day knows the date and the other guy with just the month can reason it cant be the other day than the 18th, or the guy with the day could not be certain he know the date. They would both have at least 2 choices, therefore unsolvable.
Only June 18 works.
Ive read this twenty times and still can’t deduce what the hell they are talking about or how they deduce the day.
My mind doesn’t work that way I guess.
WOn’t be using Singapore Math for our homeshool
No, I’m being dumb, the first statement gets rid of the first two months.
I’m wondering if something isn’t lost in the translation. It seems to be a problem that has more than one solution.
bernard knows months and upon understanding that albert doesn’t know, figures it out.
how?
upon finding out albert doesn’t know, bernard can rule out may and june due to uniques (18 and 19).
since he didn’t know at first, but now does, ruling out may and june leaves july and august.
since he now knows, bernard must not have ‘14’ as it’s ambiguous.
that leaves 15, 16, and 17.
since 15 and 17 are both august, but bernard knows the date... they must be eliminated.
that leaves 16th of july
july 16
I’m going with August 17. The it can’t be the 18th or 19th, because then Bernard would have known the answer because they’re unique. Since Albert knows Bernard doesn’t know, he must know that the month isn’t May or June. So all those are out. Once he says he still doesn’t know, but Bernard know does know, it must be a unique date from July or August, and August 17th is the only possibility.
Here was the answer I posted on Facebook last night.
SPOILER - don’t read this comment if you don’t want to know the answer. You’ve been warned.
Okay, right off the bat, you can eliminate the entire month of May and the entire month of June. If Cheryl had told Albert that her birthday was in May or June, then the possibility would have existed that Bernard could know the birthdate simply by knowing the day, because if Cheryl had told Bernard either the 18th or the 19th, then Bernard would have immediately known that her birthday was either May 19th or June 18th. But, Bernard didn’t know immediately, so it couldn’t have been either of those days. However when Bernard heard that Albert knew that Bernard didn’t know immediately, that gave him all the information he needed to figure out what day and month it was.
Bernard’s initial problem was that the day he was told existed in two separate months on her list, and he couldn’t differentiate between them. However, when Albert said what he did and eliminated the months of May and June, that gave Bernard the information he needed to narrow his list down to one date. There was only one date that provided such ambiguity. That date was the 16th, which could have been in May or July. Bernard wasn’t sure initially which one, but when Albert helped him to eliminate May and June completely, then Bernard knew immediately that Cheryl’s birthday was July 16th.
When Bernard stated that he now knew what her birthday was, that gave Albert the information he needed to complete the logical analysis that I just did. That’s how Albert was able to say that he now knew what the date was, even though Bernard had not told him the date.
Nope, I am wrong, because Bernard says he didnt know at first. So it cant be the 18th or 19th. So it has got to be june 17th.
That was HARD.
She was born in a cross fire hurricane and raised by a toothless bearded hag.
August 17
Uh, there is also only one 18.
since 15 and 17 are both august, but bernard knows the date... they must be eliminated.
that leaves 16th of july
WHY? just because bernard knows the date, why does that mean it couldn’t be any of these three days?
HELP!!!
May 19 is also a non-duplicate.
This type of test question perhaps explains why Singapore is among the top in math scores.
Yep. I think I was wrong again... But when I go through again I came up with the same logic you did.
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