A Math (Logic) Problem Gone Viral

Home Archive Serious Business A Math (Logic) Problem Gone Viral
ernest_t_bass's avatar

ernest_t_bass

12th Son of the Lama

24,984 posts
Apr 16, 2015 12:55 PM
[h=2]A Math problem that gone viral[/h][INDENT]A question on a quiz for teenage mathletes proved so tricky for Singapore newscaster Kenneth Kong that he posted it to Facebook to find a definitive answer. Now the problem has driven the entire country mad, and it's spreading to the rest of the world.

Here is the question:


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?
[/INDENT]
Apr 16, 2015 12:55pm
ernest_t_bass's avatar

ernest_t_bass

12th Son of the Lama

24,984 posts
Apr 16, 2015 12:56 PM
[SP]July16[/SP]
Apr 16, 2015 12:56pm
Heretic's avatar

Heretic

Son of the Sun

18,820 posts
Apr 16, 2015 1:19 PM
Hmm, so that's where Ohiobucks came up with question #1 for the upcoming sheep season week that I'll be replying to with some variation of "GFY" because shit like this makes my eyes bleed.
Apr 16, 2015 1:19pm
iclfan2's avatar

iclfan2

Reppin' the 330/216/843

6,360 posts
Apr 16, 2015 1:23 PM
July 16th? Your spoiler click thing doesn't work
Apr 16, 2015 1:23pm
ernest_t_bass's avatar

ernest_t_bass

12th Son of the Lama

24,984 posts
Apr 16, 2015 1:29 PM
iclfan2;1722060 wrote:July 16th? Your spoiler click thing doesn't work
Not sure why. How'd you come up with your answer?
Apr 16, 2015 1:29pm
Laley23's avatar

Laley23

GOAT

29,506 posts
Apr 16, 2015 1:45 PM
You can eliminate any month with a single date (no same numbers in other months).

Then, you eliminate the similar numbers in the remaining months.

Finally, you know it cannot be the month with multiple dates left. Has to be the month with only 1 date left.

I won't give the answer, but that's how it has to be solved. I don't think there is another possibility...
Apr 16, 2015 1:45pm
iclfan2's avatar

iclfan2

Reppin' the 330/216/843

6,360 posts
Apr 16, 2015 1:49 PM
I did it like laley. Couldn't be either of top 2 rows bc they have unique dates. Which leaves the bottom 2. They both share 14, so then row 3 only had one other option while 4 had 2 other options.


Sent from my iPhone using Tapatalk
Apr 16, 2015 1:49pm
SportsAndLady's avatar

SportsAndLady

Senior Member

35,632 posts
Apr 16, 2015 1:50 PM
I'll wait for footwedge to chime in before I delve into this.
Apr 16, 2015 1:50pm
iclfan2's avatar

iclfan2

Reppin' the 330/216/843

6,360 posts
Apr 16, 2015 1:51 PM
The date shows in tapatalk now instead of a spoiler message, unless it's cuz I clicked on it online. Ha too complicated with formatting.


Sent from my iPhone using Tapatalk
Apr 16, 2015 1:51pm
sleeper's avatar

sleeper

Legend

27,879 posts
Apr 16, 2015 2:00 PM
I know the answer.
Apr 16, 2015 2:00pm
J

jmog

Senior Member

6,567 posts
Apr 16, 2015 2:35 PM
I have no idea how to do a spoiler hide, so if you don't want to know how to get to July 16th, stop reading...

SPOILER ALERT!!!














The key phrase in the first statement by Albert is that he knows that Bernard doesn't know...

If Bernard had been told 19th or 18th he would know immediately what the birthday is (5/19 or 6/18). Albert only "knows" this because he knows that the month isn't May or June.

So, from the first statement you can eliminate the 5 possible answers in May and June.

When Bernard hears this, he then knows the answer, it narrowed down the months to July and August. Obviously he wouldn't yet know if he had been told the 14th as both July and August have the 14th. So his statement leaves only 3 dats, 7/16, 8/15, and 8/17.

Albert then saying he knows finalizes the solution. If it was August Albert still couldn't 'know' as there would be two dates left in August. So it has to be July 16.
Apr 16, 2015 2:35pm
ernest_t_bass's avatar

ernest_t_bass

12th Son of the Lama

24,984 posts
Apr 16, 2015 2:38 PM
jmog;1722081 wrote:(which just so happens to be my oldest son's birthday).
WTF does that have to do with anything?
Apr 16, 2015 2:38pm
1_beast's avatar

1_beast

Senior Member

5,642 posts
Apr 16, 2015 5:49 PM
Not july 16. Im going with may 19
Apr 16, 2015 5:49pm
G

gut

Senior Member

15,058 posts
Apr 16, 2015 6:35 PM
This was hard for people?

Apr 16, 2015 6:35pm
F

friendfromlowry

Senior Member

6,239 posts
Apr 16, 2015 10:25 PM
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:

Would have walked away at this point if I were Albert or Bernard
Apr 16, 2015 10:25pm
ohiobucks1's avatar

ohiobucks1

USA American

4,915 posts
Apr 16, 2015 10:58 PM
Goddamnit, you fools ruined my Sheep joke/question lol
Apr 16, 2015 10:58pm
gerb131's avatar

gerb131

Senior Member

9,932 posts
Apr 16, 2015 11:16 PM
2. The answer is 2.
Apr 16, 2015 11:16pm
Glory Days's avatar

Glory Days

Senior Member

7,809 posts
Apr 17, 2015 12:54 AM
How hot is Cheryl?
Apr 17, 2015 12:54am
W

WebFire

Go Bucks!

14,779 posts
Apr 17, 2015 9:13 AM
jmog;1722081 wrote: If Bernard had been told 19th or 18th he would know immediately what the birthday is (5/19 or 6/18). Albert only "knows" this because he knows that the month isn't May or June.
So Benard knows it's 5/19 or 6/18, but Albert knows it's not May or June.

What the fuck did I just read?
Apr 17, 2015 9:13am
sleeper's avatar

sleeper

Legend

27,879 posts
Apr 17, 2015 10:21 AM
gut;1722135 wrote:This was hard for people?

I think that's a bit unfair. I had to at least write the logic down on paper to figure it out and I'm probably the person with the highest IQ here(besides Con_Alma of course).
Apr 17, 2015 10:21am
ZWICK 4 PREZ's avatar

ZWICK 4 PREZ

Senior Member

7,733 posts
Apr 17, 2015 10:36 AM
jmog;1722081 wrote:I have no idea how to do a spoiler hide, so if you don't want to know how to get to July 16th, stop reading...

SPOILER ALERT!!!














The key phrase in the first statement by Albert is that he knows that Bernard doesn't know...

If Bernard had been told 19th or 18th he would know immediately what the birthday is (5/19 or 6/18). Albert only "knows" this because he knows that the month isn't May or June.

So, from the first statement you can eliminate the 5 possible answers in May and June.

When Bernard hears this, he then knows the answer, it narrowed down the months to July and August. Obviously he wouldn't yet know if he had been told the 14th as both July and August have the 14th. So his statement leaves only 3 dats, 7/16, 8/15, and 8/17.

Albert then saying he knows finalizes the solution. If it was August Albert still couldn't 'know' as there would be two dates left in August. So it has to be July 16.
1_beast;1722125 wrote:Not july 16. Im going with may 19

jmog literally just explained it for you lol
Apr 17, 2015 10:36am
Laley23's avatar

Laley23

GOAT

29,506 posts
Apr 17, 2015 10:55 AM
sleeper;1722259 wrote:I think that's a bit unfair. I had to at least write the logic down on paper to figure it out and I'm probably the person with the highest IQ here(besides Con_Alma of course).
Took me a good amount of time as well.
Apr 17, 2015 10:55am
W

WebFire

Go Bucks!

14,779 posts
Apr 17, 2015 10:57 AM
Laley23;1722281 wrote:Took me a good amount of time as well.
Not to mention that there isn't anybody that would be able to figure this out by only having the conversation above with someone.
Apr 17, 2015 10:57am
Laley23's avatar

Laley23

GOAT

29,506 posts
Apr 17, 2015 11:01 AM
WebFire;1722283 wrote:Not to mention that there isn't anybody that would be able to figure this out by only having the conversation above with someone.
??? I think we are to assume that the 2 hold a conversation about what they are told.
Apr 17, 2015 11:01am
W

WebFire

Go Bucks!

14,779 posts
Apr 17, 2015 11:07 AM
Laley23;1722285 wrote:??? I think we are to assume that the 2 hold a conversation about what they are told.
Point is, if this conversation was held in real life as it is above, no one would know the answer.
Apr 17, 2015 11:07am