Geekzone: technology news, blogs, forums
Guest
Welcome Guest.
You haven't logged in yet. If you don't have an account you can register now.


Batman

Mad Scientist
29763 posts

Uber Geek

Trusted
Lifetime subscriber

#171343 14-Apr-2015 16:53
Send private message



I don't get it.

1) 2 separate persons got told each the month, the other the day of a birthday.

2) A states he doesn't know the birthday but he is sure B doesn't know.

3) B says he knows the birthday.

4) A deduces if B knows then A must know it too.

WTF

Filter this topic showing only the reply marked as answer View this topic in a long page with up to 500 replies per page Create new topic
 1 | 2 | 3
Batman

Mad Scientist
29763 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283060 14-Apr-2015 16:53
Send private message

http://www.straitstimes.com/sites/straitstimes.com/files/20150413/math1e.jpg


SINGAPORE - A Primary school mathematics question has been making the rounds on Facebook and stirring up debate ...

...
In case you're wondering, it turns out it is a "scholarship level-type exam"





kendo
213 posts

Master Geek


  #1283069 14-Apr-2015 17:06
Send private message

Judging by the poor grammar I think it was either translated incorrectly or made up with no real answer.

tripp
3848 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283070 14-Apr-2015 17:07
Send private message

bloody woman and their mind games (kidding).

Who the hell wants to be friends with someone that does this sh** :P



NonprayingMantis
6434 posts

Uber Geek


  #1283077 14-Apr-2015 17:17
Send private message

think about the reverse logic and the list of potential answers.

If Albert states he doesn't know, but that he also knows that Bernard doesn't know,  then that narrows down the list for Bernard to consider

say, for example, the date was 19th May.  If bernard had been told  "it's the19th", then he would know the answer was 19th May.
So for Albert, who only knows the month, to confidently state Bernard doesn't know,  Albert MUST know the month is one of the months that doesn't contain a unique number.  (if it wasn't, he couldn't be sure Bernard didn't know) therefore it can't be June or May.  and so must be July or August.

Bernard initially doesn't know, but when Albert states that he knows Bernard doesn't know,  then Bernard knows that the correct month must be one without a unique date. (July or August).  That is the only way for Albert to correctly state that he knows Bernard doesn't know.

So now Bernard knows's that it must be July or August. For him to state that he now knows the answer, it MUST be one of the dates that doesn't appear in both July and August, i.e. 16th, 15th, or 17th.  Since there are two options (15th 17th) for august, but only 1 for July (16ht), for him to state he now knows the correct month, it MUST be July.

so the answer is 16th July.  It's the only date option for which these statements can all be correct.

semigeek
1606 posts

Uber Geek


  #1283080 14-Apr-2015 17:20
Send private message

NonprayingMantis: think about the reverse logic and the list of potential answers.

If Albert states he doesn't know, but that he also knows that Bernard doesn't know,  then that narrows down the list for Bernard to consider

say, for example, the date was 19th May.  If bernard had been told  "it's the19th", then he would know the answer was 19th May.
So for Albert, who only knows the month, to confidently state Bernard doesn't know,  Albert MUST know the month is one of the months that doesn't contain a unique number.  (if it wasn't, he couldn't be sure Bernard didn't know) therefore it can't be June or May.  and so must be July or August.

Bernard initially doesn't know, but when Albert states that he knows Bernard doesn't know,  then Bernard knows that the correct month must be one without a unique date. (July or August).  That is the only way for Albert to correctly state that he knows Bernard doesn't know.

So now Bernard knows's that it must be July or August. For him to state that he now knows the answer, it MUST be one of the dates that doesn't appear in both July and August, i.e. 16th, 15th, or 17th.  Since there are two options for august, but only 1 for July, for him to state he now knows the correct month, it MUST be July.

so the answer is 17th July.  It's the only date option for which these statements can all be correct.


Close, it's July 16


Sideface
9357 posts

Uber Geek

Trusted
DR
Lifetime subscriber

  #1283081 14-Apr-2015 17:22
Send private message

NonprayingMantis: think about the reverse logic and the list of potential answers.

If Albert states he doesn't know, but that he also knows that Bernard doesn't know,  then that narrows down the list for Bernard to consider

say, for example, the date was 19th May.  If bernard had been told  "it's the19th", then he would know the answer was 19th May.
So for Albert, who only knows the month, to confidently state Bernard doesn't know,  Albert MUST know the month is one of the months that doesn't contain a unique number.  (if it wasn't, he couldn't be sure Bernard didn't know) therefore it can't be June or May.  and so must be July or August.

Bernard initially doesn't know, but when Albert states that he knows Bernard doesn't know,  then Bernard knows that the correct month must be one without a unique date. (July or August).  That is the only way for Albert to correctly state that he knows Bernard doesn't know.

So now Bernard knows's that it must be July or August. For him to state that he now knows the answer, it MUST be one of the dates that doesn't appear in both July and August, i.e. 16th, 15th, or 17th.  Since there are two options for august, but only 1 for July, for him to state he now knows the correct month, it MUST be July.

so the answer is 17th July.  It's the only date option for which these statements can all be correct.


This sounds like something from Yes Minister.  smile




Sideface


NonprayingMantis
6434 posts

Uber Geek


  #1283084 14-Apr-2015 17:24
Send private message

semigeek:
NonprayingMantis: think about the reverse logic and the list of potential answers.

If Albert states he doesn't know, but that he also knows that Bernard doesn't know,  then that narrows down the list for Bernard to consider

say, for example, the date was 19th May.  If bernard had been told  "it's the19th", then he would know the answer was 19th May.
So for Albert, who only knows the month, to confidently state Bernard doesn't know,  Albert MUST know the month is one of the months that doesn't contain a unique number.  (if it wasn't, he couldn't be sure Bernard didn't know) therefore it can't be June or May.  and so must be July or August.

Bernard initially doesn't know, but when Albert states that he knows Bernard doesn't know,  then Bernard knows that the correct month must be one without a unique date. (July or August).  That is the only way for Albert to correctly state that he knows Bernard doesn't know.

So now Bernard knows's that it must be July or August. For him to state that he now knows the answer, it MUST be one of the dates that doesn't appear in both July and August, i.e. 16th, 15th, or 17th.  Since there are two options for august, but only 1 for July, for him to state he now knows the correct month, it MUST be July.

so the answer is 17th July.  It's the only date option for which these statements can all be correct.


Close, it's July 16



damn typo in the last sentence :P

 
 
 

Trade NZ and US shares and funds with Sharesies (affiliate link).
Behodar
10508 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283086 14-Apr-2015 17:27
Send private message

Sideface: This sounds like something from Yes Minister.  smile

No, it doesn't. Stuff from Yes Minister actually makes sense after you think about it! tongue-out

Batman

Mad Scientist
29763 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283096 14-Apr-2015 17:44
Send private message

NonprayingMantis: think about the reverse logic and the list of potential answers.

If Albert states he doesn't know, but that he also knows that Bernard doesn't know,  then that narrows down the list for Bernard to consider

say, for example, the date was 19th May.  If bernard had been told  "it's the19th", then he would know the answer was 19th May.
So for Albert, who only knows the month, to confidently state Bernard doesn't know,  Albert MUST know the month is one of the months that doesn't contain a unique number.  (if it wasn't, he couldn't be sure Bernard didn't know) therefore it can't be June or May.  and so must be July or August.

Bernard initially doesn't know, but when Albert states that he knows Bernard doesn't know,  then Bernard knows that the correct month must be one without a unique date. (July or August).  That is the only way for Albert to correctly state that he knows Bernard doesn't know.

So now Bernard knows's that it must be July or August. For him to state that he now knows the answer, it MUST be one of the dates that doesn't appear in both July and August, i.e. 16th, 15th, or 17th.  Since there are two options (15th 17th) for august, but only 1 for July (16ht), for him to state he now knows the correct month, it MUST be July.

so the answer is 16th July.  It's the only date option for which these statements can all be correct.


ah, it makes sense :D

Geektastic
17943 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283098 14-Apr-2015 18:01
Send private message

joker97:

I don't get it.

1) 2 separate persons got told each the month, the other the day of a birthday.

2) A states he doesn't know the birthday but he is sure B doesn't know.

3) B says he knows the birthday.

4) A deduces if B knows then A must know it too.

WTF


Ignoring the actual question, the English is a disgrace.





Rickles
2937 posts

Uber Geek

Trusted

  #1283119 14-Apr-2015 18:08
Send private message

   >Albert MUST know the month is one of the months that doesn't contain a unique number.<

Huh?  How is that deduced?  What's a 'unique' number (I thought they all were)?

Batman

Mad Scientist
29763 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283123 14-Apr-2015 18:12
Send private message

because otherwise Bernard will know the date just by looking at the list, but he could not, so it can't be the 19th or 18th as they are standalone dates

Rickles
2937 posts

Uber Geek

Trusted

  #1283127 14-Apr-2015 18:23
Send private message

To quote your original post, WTF?

Batman

Mad Scientist
29763 posts

Uber Geek

Trusted
Lifetime subscriber

  #1283145 14-Apr-2015 19:04
Send private message

and I presume since two digit numbers are involved, this is somehow a maths question with questionable grammar

kendo
213 posts

Master Geek


  #1283150 14-Apr-2015 19:12
Send private message

NonprayingMantis: think about the reverse logic and the list of potential answers.

If Albert states he doesn't know, but that he also knows that Bernard doesn't know,  then that narrows down the list for Bernard to consider

say, for example, the date was 19th May.  If bernard had been told  "it's the19th", then he would know the answer was 19th May.
So for Albert, who only knows the month, to confidently state Bernard doesn't know,  Albert MUST know the month is one of the months that doesn't contain a unique number.  (if it wasn't, he couldn't be sure Bernard didn't know) therefore it can't be June or May.  and so must be July or August.

 

Why cant it be June or May? It cant be the 2 unique dates sure, but how can he be sure that its not one of the other dates in those months that are shared with other months?

 1 | 2 | 3
Filter this topic showing only the reply marked as answer View this topic in a long page with up to 500 replies per page Create new topic





News and reviews »

Air New Zealand Starts AI adoption with OpenAI
Posted 24-Jul-2025 16:00


eero Pro 7 Review
Posted 23-Jul-2025 12:07


BeeStation Plus Review
Posted 21-Jul-2025 14:21


eero Unveils New Wi-Fi 7 Products in New Zealand
Posted 21-Jul-2025 00:01


WiZ Introduces HDMI Sync Box and other Light Devices
Posted 20-Jul-2025 17:32


RedShield Enhances DDoS and Bot Attack Protection
Posted 20-Jul-2025 17:26


Seagate Ships 30TB Drives
Posted 17-Jul-2025 11:24


Oclean AirPump A10 Water Flosser Review
Posted 13-Jul-2025 11:05


Samsung Galaxy Z Fold7: Raising the Bar for Smartphones
Posted 10-Jul-2025 02:01


Samsung Galaxy Z Flip7 Brings New Edge-To-Edge FlexWindow
Posted 10-Jul-2025 02:01


Epson Launches New AM-C550Z WorkForce Enterprise printer
Posted 9-Jul-2025 18:22


Samsung Releases Smart Monitor M9
Posted 9-Jul-2025 17:46


Nearly Half of Older Kiwis Still Write their Passwords on Paper
Posted 9-Jul-2025 08:42


D-Link 4G+ Cat6 Wi-Fi 6 DWR-933M Mobile Hotspot Review
Posted 1-Jul-2025 11:34


Oppo A5 Series Launches With New Levels of Durability
Posted 30-Jun-2025 10:15









Geekzone Live »

Try automatic live updates from Geekzone directly in your browser, without refreshing the page, with Geekzone Live now.



Are you subscribed to our RSS feed? You can download the latest headlines and summaries from our stories directly to your computer or smartphone by using a feed reader.