Monday puzzle: the efficient drink order
Today's puzzle has a special extra. Because the problem is geometric in nature, I thought it would be fun to make a video of the puzzle on Youtube. Here is a link to the puzzle videos on Youtube. Efficient drink order problem - Youtube (it's just over at minute at 1 min 18 ...

A location game on a triangle
A father bequeaths a triangular piece of land to his children, Alice and Bob. The father was known to be quirky, and in his will, he specified a rather unusual way for the land to be divided. On a map of the land, Bob is to mark a location of his choosing. ...

Monday puzzle: fruit label stickers
This is a problem slightly modified from a 2002 Putnam competition question. I thought about this problem while eating a large grapefruit one morning. The puzzle Imagine a perfectly round grapefruit that is labeled with 5 fruit stickers. Prove that the grapefruit can be cut in two equal halves in which one of the ...

Monday puzzle: the moat crossing problem
This is a fun geometrical puzzle--refer to the picture below. Here is the problem:

Puzzle: ant and honey
The shortest distance between two points on a plane is a straight line. But finding the shortest distance on other surfaces is a more interesting problem. Here is a puzzle that is harder than it sounds:

Video: the “hardest” geometry problem in the world
Rushmore is a rather quirky but interesting movie that came out in 1998. One of the scenes I particularly enjoyed is about the main character doing a mathematical proof. During class, Max Fischer asks the teacher about a math problem written on the board. The teacher explains the problem is a joke: ...

Puzzle: who wins this dart game?
Alice and Bob play the following game with their friend Charlie. Charlie begins the game by secretly picking a spot on the dartboard. The spot can be anywhere on the board, but once picked it does not change. Then Alice and Bob each get to throw one dart at the board. At this ...

Geometry puzzle: string cutting game
This is a great problem I came across, and I'd love to see it used as a consulting or technical interview question. Here is the setup. An interviewer gives you a string that measures 4 meters in length. The string is to be cut into two pieces. One piece is made into ...

One mile south, one mile east, one mile north – a classic puzzle
I was having dinner with a friend the other day. We were talking about my writing, and out of the blue he asked me what my favorite puzzle was. A lot of the puzzles I wrote about on this site came to mind, including The hat puzzle A mystery Sherlock Holmes couldn't solve, ...

A math puzzle about splitting land
A father is splitting up land among his two sons in estate planning. How can he divide the land fairly? One approach is to split the land evenly. But even this method can get complicated if we add some realistic assumptions. Today's puzzle illustrates why splitting land can be a mind-boggling ...