Riddles are fun. This post is for you Phillip. :)
I've figured out the first two easily enough (<3 min of thinking). I'll post the answers in the comments section of this post. The third I am still pondering although the answer is also available. I've taken this from another blogger I happened across. I always wonder where my common sense for riddles comes from since lack it so often in everyday life, where it would actually be useful...
Stephanie takes the Caltrain every afternoon to go home. From the Palo Alto train station, she can either go north to San Francisco or south to Mountain View. Both north and south trains arrive at the station every 10 minutes. Instead of deciding which train to take everyday, Stephanie decides to place her destination in the hands of fate and resolves to arrive at the Palo Alto station at random times between the hours of 4-6 p.m. and to take the first train that reaches the platform (only one platform). However, after a few weeks, Stephanie realizes that 9/10 times, she takes the San Francisco train from Stanford. How can this be?
The Davis lab used to have a lot of Swedish post-docs. Let's pretend that the PI was in Sweden when 4 postdocs -- Simon, Fredrik, Bob, and Johan -- ask the PI for lab positions in the States. The PI has 2 black hats and 2 white hats. He distributes the hats randomly to the four postdocs and takes them to the men's restroom (Joe invented this scenario, not me). The man cannot see which hat they are wearing. He places one postdoct in the bathroom stall, and no one can see in or out of this stall. The other 3 postdocs are lined up vertically facing the wall of the stall, and can see the hats in front of them (see Figure 1). The PI says that whoever can tell which hat they are wearing can come to Stanford. There is a LONG PAUSE before one man speaks up. Which man correctly guesses which hat he is wearing (black or white) and why?
The Mafia sends you into a completely dark room. On the table, there is a full deck of cards, randomly shuffled. The black cards are all face-up, and the red cards are all face-down. You must separate the card deck into two equal piles (26 cards in each pile) and manipulate the deck so that the same number of cards are facing "up" in each pile. You may flip cards over. How do you solve the puzzle?
6 comments:
The northern train always arrives at the station 1 minute before the southern train...every 10 minutes
The man in the stall cannot see anyone else, he is isolated and therefore cannot tell for certain which hat he is wearing. So forget about the man in the stall. The man closest to the stall is also blind to any hats, so he must also be excluded. At first glance, the man farthest away from the stall should be able to tell which hat he is wearing because he can see the hats of the two men in front of him. This would be the case if he saw two white hats, for example, and can safely say that he is wearing a black hat. However, there is a long silence. The two men in front of him must be wearing a white and a black hat. Then, the man in the middle (of the 3 outside) can deduce that the outside man cannot tell which hat he is wearing...which means that if the man in front of him is wearing a white hat (for example), then the middle man knows that he must be wearing the opposite...a black hat (for example).
bah i was totally gonna say that because from personal experience i have found it true. I hate the 1 minute gap.
I think the dude in the stall would be way faster. If no one can see him, why can't he just take it off and look at the damn thing himself? (He eventually gets antsy in the stall after a long pause and rips it off, triumphantly declaring its color.)
haha because it's a thought experiment!
i think nosugrefneb wins the position at Stanford.
ah! i got it. count out 26 cards and put them in the pile. then flip the other 26 over. done.
that one was much harder than the first two.
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