The Riddler at FiveThirtyEight site

A forum for good logic/math puzzles.

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Anonymous37
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The Riddler at FiveThirtyEight site

Postby Anonymous37 » Sat Mar 19, 2016 7:32 pm UTC

This isn't a specific logic puzzle, but I wanted to note that FiveThirtyEight has a weekly logic puzzle. The archives can be found by going to the site and typing "The Riddler" into the search box; there's been about 12 or 13 so far.

One of these is the "dropping cellphones out of windows on a 100-story building puzzle" that's been here, but the majority are ones that I haven't seen before, with some interesting variations provided by the readers. Enjoy.

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thunk
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Re: The Riddler at FiveThirtyEight site

Postby thunk » Sun Jun 12, 2016 6:54 am UTC

This week's Riddler is of course, a restatement of the infamous Blue-Eyed Islander problem that Randall popularized.
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Xias
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Re: The Riddler at FiveThirtyEight site

Postby Xias » Tue Jun 14, 2016 2:25 pm UTC

thunk wrote:This week's Riddler is of course, a restatement of the infamous Blue-Eyed Islander problem that Randall popularized.


I enjoy this iteration of the puzzle quite a bit. The situation, where they all gossip about each other, helps create the "They always see each other's eyes" rule while making it relate to a real life situation. Everyone is familiar with gossip.

The twitter replies also indicate that this puzzle causes just as much fuss as the original.

Nork
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Re: The Riddler at FiveThirtyEight site

Postby Nork » Mon Jun 20, 2016 3:28 pm UTC

Fivethirtyeight got it wrong, though:
Spoiler:
Presumably, one of the mathematicians is the head of the department. As soon as he hears the initial statement, he posts a job posting for mathematicians who are willing to start in 9 weeks (He figures they'll all leave together because he's familiar with this type of puzzle. He assumes it's 9 weeks because he thinks he hasn't made any mistakes).

Unfortunately for him, he has made mistakes, so the others are all checking the job postings for the chance to apply for his job. When they see the nine week start date and realize he doesn't think he's made any mistakes, they can infer that they've all made mistakes. They all resign at the end of week 1.

When the head of the department sees all of them resign at the end of week 1, he realizes they were vying for his job, which means he made a mistake, so he resigns at the end of week 2.


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