Are you as smart as a primary school kid?
EDIT: after all, this was not for primary school kids. It was for a math olympiad, in Singapore, for 14/15 year olds...
Previous iteration: #728017
pull down to refresh
131 sats \ 4 replies \ @030e0dca83 2 Apr
Let me guess: answer is July 14.
It's not may or June because there is possibility birthday can be may 19 or June 18, in this case Bernard would know the answer but he doesn't.
Now we have July or August, so we need similar numbers in this couple (Bernard has to choose between two months), and it's 14. Now when Bernard got information that Alberts doesn't know either it's 14 or 16 we came to the answer. It's July 14
reply
0 sats \ 3 replies \ @Undisciplined 2 Apr
I'm still missing something, because it seems like Bernard would know the date for the 15th, 16th, or 17th, but him knowing wouldn't help Albert.
And, it seems like he doesn't have enough information to know the month if it's a 14th.
reply
34 sats \ 2 replies \ @030e0dca83 2 Apr
Yes now with help I found flaw in my calculations. The answer is Jule 16.
Bernard has to pairs on months with similar numbers:
- May July
- July August
When Bernard got information from Albert that he 100% should know the answer we take pair with unique number (May July), and it can't be May. So the answer is July 16
reply
8 sats \ 1 reply \ @Undisciplined 2 Apr
That's what I was leaning towards, but I still don't totally see it. More coffee.
reply
41 sats \ 0 replies \ @030e0dca83 2 Apr
At some point there's an option with 15 may or 15 august, but as Bernard final statement "I didn't know but now know", he shoude choose from month with to numbers this month is July.
reply
108 sats \ 1 reply \ @SimpleStacker 2 Apr
This is trickier than it seems.
By statement 1, A needs to know that B doesn't know. How? Well, B can only know for sure if B sees an 18 or 19.
- If A sees May, B could have 15, 16, or 19. If it's 19, B would definitely know. Thus it can't be May.
- If A sees June, B could have 17 or 18, so it can't be June.
- If A sees July, B could have 14 or 16, so it could be July.
- If A sees August, B could have 14, 15, or 17 so it could be August.
By statement 2, B must now know. B knows it could only be July or August.
- If B had 14, he wouldn't be able to know still.
- If B has 16, he knows it's July 16. If B has 15 or 17, he knows it's August 15 or August 17.
By statement 3, A must now know.
- If B had 15 or 17 and A had August, A still wouldn't know the exact date in August.
- Therefore, it must be July 16.
WHEW
reply
0 sats \ 0 replies \ @030e0dca83 2 Apr
Finally. We collectively solve it
reply
100 sats \ 0 replies \ @WeAreAllSatoshi 2 Apr
I think it’s July 16, but I don’t have time to explain my rationale right now. And I swear I didn’t look at others answers first
reply
100 sats \ 4 replies \ @Undisciplined 2 Apr
June 17th
If it were June 18th, then Albert would have already known. Bernard, knowing it's June and knowing it's not the 18th, knows it must be the 17th.
Bernard knowing the date, tells Albert that it's not August, so it must be June.
reply
37 sats \ 3 replies \ @030e0dca83 2 Apr
How would Albert know if he only knows the month and not the day?
reply
8 sats \ 2 replies \ @Undisciplined 2 Apr
If Albert knows it's one of the 17th's then it's either June or August. If it were August, then Albert not knowing wouldn't be enough information for Bernard to deduce anything, because it could be any of the August dates.
Albert not knowing only eliminates the 18th and 19th as possible days, since they're the only ones unique to a month.
Eliminating the 19th would still leave two possibilities for May, so Albert knows it's not May.
The fact that Bernard can infer the answer means the date is from the month reduced to one option.
reply
42 sats \ 1 reply \ @030e0dca83 2 Apr
Ok, now my turn.
In the Albert eyes:
May 33% possibility Bernard knows the answers (because of unique 19)
June 50% Bernard knows (because of unique 18)
July 0% (there's no unique numbers)
August 0% (no unique numbers).
If Alberts says: Bernard doesn't know answer (read 0% chance) we need months without unique numbers.
Everything else you can follow in my first comment below
reply
0 sats \ 0 replies \ @Undisciplined 2 Apr
Lol, I mixed up who knows what.
So, they can cross off May and June. But, then if Bernard knows it's a 14th, he still wouldn't know which month.
reply
0 sats \ 0 replies \ @WeAreAllSatoshi 2 Apr
But also, what’s the deal with Cheryl?
reply