I gave a short talk about my favorite math jokes at G4G15. G4G stands for the Gathering for Gardner, my favorite conference. Here is a joke about Heisenberg from my talk. * * * Heisenberg gets pulled over on the highway. Cop: “Do you know how fast you were going, sir?” Heisenberg: “No, but I know exactly where I am.” After my talk, David Albert sent me a sequel to this joke. * * * Heisenberg gets pulled over on the highway. Cop: “Do you know how fast you were going, sir?” Heisenberg: “No, but I know exactly where I am.” Cop: “You were going 85 miles per hour”. Heisenberg: “Oh great—now I’m los ..read more

Another cute geometry puzzle was posted on Facebook. Puzzle. An equilateral triangle in a plane has three vertices with known x-coordinates: a, b, and c. What is the side of the triangle? I want to describe three different solutions that the readers of the Facebook channel posted. But before doing so, let’s look at the problem’s symmetries. We can immediately say that the answer should be a symmetric function of three variables: |a-b|, |b-c|, and |c-a|. It is possible to coordinate-bash the problem. However, I always prefer geometric solutions. Having said that, if one wants a calculation, u ..read more

The homework I give to my students (who are in 6th through 9th grades) often starts with a math joke related to the topic. Once, I decided to let them be the comedians. One of the homework questions was to invent a math joke. Here are some of their creations. Two of my students decided to restrict themselves to the topic we studied that week: sorting algorithms. The algorithm jokes are at the end. * * * A binary integer asked if I could help to double its value for a special occasion. I thought it might want a lot of space, but it only needed a bit. * * * Everyone envies the circle. It is well ..read more

Here is an interesting puzzle by Ivan Mitrofanov. Puzzle. In front of my dog, Fudge, lies an infinite number of meatballs with a fly sitting on each of them. At each move, Fudge makes two consecutive operations described below. Eats a meatball and all the flies sitting on it at that time. Transfers one fly from one meatball to another (there can be as many flies as you want on a meatball). Fudge wants to eat no more than a million flies. Assuming that flies sit still, prove that Fudge doesn’t have a strategy where each meatball is eaten at some point. Share ..read more

I collect math jokes and, of course, show them to my family. From time to time, my family contributes. The first joke is by my son, Alexey. * * * When you board a train traveling East from Chicago to Boston at 60 miles an hour, you realize you are a part of the problem. And this one is one of mine. * * * A dyslexic’s excuse: my god ate my homework. My grandson, Alex, heard the following famous joke. * * * A logician rides an elevator. The door opens, and someone asks: —”Are you going up or down?” —”Yes.” He created his own version. * * * A logician rides an elevator. The door opens, and ..read more

These two puzzles were given to me by Andrey Khesin. Puzzle. My friend and I are going to play the following game at a casino. Each round, each of us (my friend, the dealer, and I) secretly chooses a black or white stone and drops it in the same bag. Then, the contents of the bag are revealed. If all three stones are the same color, my friend and I win the round. If not, we lose to the dealer. One extra caveat. I have a superpower: as soon as we sit down, I can read the dealer’s mind and learn the dealer’s choices for all future rounds. Unfortunately, at that time, it’s too late for me to giv ..read more

* * * —Why was the fraction worried about marrying the decimal? —Because he would have to convert. * * * —How does a professional mathematician plow a field? —With a protractor. * * * —How many bakers does it take to bake a pi? —3.14. * * * —What did the witch doctor say after lifting the curse? —Hexagon. * * * —What do you call a teapot of boiling water on top of a mountain? —A high-pot-in-use. * * * —What do you call a K1 graph drawn at freezing temperature? —An ice-olated vertex! Share ..read more

* * * —What is the best way to pass a geometry test? —Know all the angles. * * * —Did you hear about the over-educated circle? —It has 360 degrees! * * * —What do parallel lines and vegetarians have in common? —They never meat. * * * —Did you hear about the mathematician who’s afraid of negative numbers? —He’ll stop at nothing to avoid them. * * * —What do you call a gentleman who spent all the summer at the beach? —A tangent. * * * —What do mathematicians and the Air Force have in common? —They both use pi-lots. * * * —Why can’t a nose be 12 inches long? —Because then it would be a foot ..read more

There are a lot of puzzles where you need to guess something asking only yes-or-no questions. In this puzzle, there are not two but three possible answers. Puzzle. Mike thought of one of three numbers: 1, 2, or 3. He is allowed to answer “Yes”, “No”, or “I don’t know”. Can Pete guess the number in one question? Yes, he can. This problem was in one of my homeworks, and my students had a lot of ideas. Here is the first list were ideas are similar to each other. I am thinking of an odd number. Is my number divisible by your number? If I were to choose 1 or 2, would your number be bigger than m ..read more

I rarely post physics puzzles, but this one is too good to pass on. Puzzle. A wireframe icosahedron is assembled so that each of its edges has a resistance of 1. What is the total resistance between opposite vertices of the icosahedron? While we are at it, another interesting question would be the following. Puzzle. A wireframe cube is assembled so that each of its edges has a resistance of 1. What is the total resistance between opposite vertices of the cube? And this reminds me of a question I heard when I was preparing for an IMO many years ago. Puzzle. A wireframe infinite square grid ..read more