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Duck Rocks
After a long night of frivolous quackery, two delirious ducks are having a difficult time finding each other in their pond. The pond happens to contain a 3×3 grid of rocks. Every minute, each duck ran...
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Three Birthdays
The classic birthday problem asks about how many people need to be in a room together before you have better-than-even odds that at least two of them have the same birthday. Ignoring leap years, the a...
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Hector's Puzzled - Attempts at solving fivethirtyeight.com Riddlers.
about other people's problems.
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Spelling Bee
The New York Times recently launched some new word puzzles, one of which is Spelling Bee. In this game, seven letters are arranged in a honeycomb lattice, with one letter in the center. The goal is to...
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Century Product
Given any three random integers — X, Y and Z — what are the chances that their product is divisible by 100? (fivethirtyeight) Solution Reading the question charitably (since “random integer” has no sp...
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Packing Spheres
What’s the smallest tetrahedron into which we can pack four spheres? (fivethirtyeight.com) Solution I’ll assume without proof what seems obvious, namely, that the optimal configuration of the spheres ...