OT: When is Cheryl's Birthday? (A math problem/riddle)

HarthorneWingo · Post #1 » by **HarthorneWingo** » Tue Apr 14, 2015 8:12 pm

http://www.nytimes.com/2015/04/15/scien ... 22000&_r=0

SaveUsKP6 · Post #2 » by **SaveUsKP6** » Tue Apr 14, 2015 8:21 pm

Screw the math... whoever wrote this needs to brush up their grammar.

Rasho Brezec · Post #3 » by **Rasho Brezec** » Tue Apr 14, 2015 8:27 pm

July 16.

Spoiler:

Post #4 » by **Capn'O** » Tue Apr 14, 2015 8:28 pm

Spoiler:

E-Balla · Post #5 » by **E-Balla** » Tue Apr 14, 2015 8:28 pm

How is that possibly a math problem? Are people really that far removed from school that they forgot the difference between riddles and math problems?

HarthorneWingo · Post #6 » by **HarthorneWingo** » Tue Apr 14, 2015 8:29 pm

Capn'O wrote:
Spoiler:
NM - under construction...

HarthorneWingo · Post #7 » by **HarthorneWingo** » Tue Apr 14, 2015 8:31 pm

E-Balla wrote:How is that possibly a math problem? Are people really that far removed from school that they forgot the difference between riddles and math problems?

The NY Times said "math problem" so I wrote "math problem." But I don't want to f*ck up your day so I'm going to change it. Sheesh.

Rasho Brezec · Post #8 » by **Rasho Brezec** » Tue Apr 14, 2015 8:31 pm

E-Balla wrote:How is that possibly a math problem? Are people really that far removed from school that they forgot the difference between riddles and math problems?

It's a logic problem, which was always a part of maths curriculum, at least in Europe.

melomax · Post #9 » by **melomax** » Tue Apr 14, 2015 8:32 pm

100% not may 19 or june 18

Trav_NYK · Post #10 » by **Trav_NYK** » Tue Apr 14, 2015 8:34 pm

Spoiler:

melomax · Post #11 » by **melomax** » Tue Apr 14, 2015 8:34 pm

for that matter, it doesnt make sense for it to be at any of the june or may dates period..

E-Balla · Post #12 » by **E-Balla** » Tue Apr 14, 2015 8:35 pm

HarthorneWingo wrote:
E-Balla wrote:How is that possibly a math problem? Are people really that far removed from school that they forgot the difference between riddles and math problems?

The NY Times said "math problem" so I wrote "math problem." But I don't want to f*ck up your day so I'm going to change it. Sheesh.

I was referring to the NY Times writer...

HarthorneWingo · Post #13 » by **HarthorneWingo** » Tue Apr 14, 2015 8:35 pm

melomax wrote:100% not may 19 or june 18

why?

melomax · Post #14 » by **melomax** » Tue Apr 14, 2015 8:36 pm

ok i think its one of the july dates. 14 or 16.

probably 16.

melomax · Post #15 » by **melomax** » Tue Apr 14, 2015 8:37 pm

HarthorneWingo wrote:
melomax wrote:100% not may 19 or june 18

why?

because they dont repeat, and bernard 100% doesnt know the *full* birthday

if she told bernard 19 or 18 he would know the date.

melomax · Post #16 » by **melomax** » Tue Apr 14, 2015 8:40 pm

ok now im not sure its 16, but its definitely either july 14 or 16 100% imo.

Trav_NYK · Post #17 » by **Trav_NYK** » Tue Apr 14, 2015 8:41 pm

melomax wrote:
HarthorneWingo wrote:
melomax wrote:100% not may 19 or june 18

why?

because they dont repeat, and bernard 100% doesnt know the *full* birthday

if she told bernard 19 or 18 he would know the date.

thats why it has to be either one

E-Balla · Post #18 » by **E-Balla** » Tue Apr 14, 2015 8:42 pm

Rasho Brezec wrote:July 16.

Spoiler:
Step 1: can't be May or June, because they have days 18 and 19, and Albert knows that Bernard doesn't know those
Step 2: can't be 14, because Bernard knows the day and 14 is in both July and August
Step 3: can't be August, because by now, both of them know the date, and August still has days 15 and 17 left

What I got.

melomax · Post #19 » by **melomax** » Tue Apr 14, 2015 8:44 pm

ok im with you guys, its gotta be 16

melomax · Post #20 » by **melomax** » Tue Apr 14, 2015 8:48 pm

Trav_NYK wrote:
melomax wrote:
HarthorneWingo wrote:
why?

because they dont repeat, and bernard 100% doesnt know the *full* birthday

if she told bernard 19 or 18 he would know the date.

thats why it has to be either one

no albert says bernard 100% does not know the full birth date

if cheryl told bernard 18 or 19 as the date, bernard would 100% know it was either may 19 or june 18. its a non starter, bernard 100% cannot know its either of those dates.

and from that information, we can be also sure that it is impossible for the FULL birthdate to be either from may or june.

and so we are left with

july 14 16
august 14 15 17

since august 15, 17, match up with dates also seen in may and june, we can be 100% sure that it cannot be 15 or 17.

thus we are left with

july 14, 16
august 14

since is impossible to infer the difference between august 14 and july 14, i guess ill pick july 16.