Math Fun Facts are cool ideas and neat puzzles that will stretch your brain and change the way you think. http://www.math.hmc.edu/funfacts/ www.math.hmc.edu/funfacts/http://www.math.hmc.edu/funfacts/addbutton/MovingButton.GIFSubscribe with My Yahoo!Subscribe with NewsGatorSubscribe with My AOLSubscribe with BloglinesSubscribe with NetvibesSubscribe with GoogleSubscribe with PageflakesSubscribe to this feed to see Math Fun Facts that have recently been added or modified. Consider N equally spaced on points on the unit circle, with the point P=(1,0) as one of these equally spaced points, and draw (N-1) chords from P to every other point. In Chords on a Unit Circle, we saw that the product of the lengths of these chords was just N. But what happens if we stretch this circle so that it is an ellipse? ... http://www.math.hmc.edu/funfacts/ffiles/20008.2.shtml Take N equidistant points on the unit circle. Pick one of... http://www.math.hmc.edu/funfacts/ffiles/20001.1-2-3.shtml How good is your intuition in high dimensions? Take a square and divide it into its four quadrants. Inscribe a circle in each. Now, draw a circle whose center is at the center of the big square and whose radius is just big enough to touch the four circles you just drew. We can perform an equivalent operation in a cube, inscribing spheres in each of its eight octants and then placing a sphere in the middle, just large enough to touch the other spheres.... http://www.math.hmc.edu/funfacts/ffiles/20007.2.shtml In Seven Shuffles we saw that it takes about... http://www.math.hmc.edu/funfacts/ffiles/20001.4-6.shtml If you liked the Fun Fact Multiplication by 11, you'll enjoy seeing how to take that idea one step farther. Here's a quick way to multiply by 111.... http://www.math.hmc.edu/funfacts/ffiles/20002.1.shtml Multiplication by 11 is easy! To multiply by a 2-digit number add the two digits... http://www.math.hmc.edu/funfacts/ffiles/10001.1.shtml The digits of Pi are fascinating. As the ratio of the circumference of a circle to its diameter,... http://www.math.hmc.edu/funfacts/ffiles/10001.2-8.shtml You put a deck of cards in your pocket, and invite anyone in the audience to call out a number between 1 and 15. Then you reach into your pocket, you take out a set of cards whose sum is the number that was called!... http://www.math.hmc.edu/funfacts/ffiles/10003.5-8.shtml If you've seen the Banach-Tarski paradox, you know that it is possible to cut a solid 3-dimensional ball into 5 pieces and reassemble the pieces using only rigid motions to form two solid balls each the same size as the original. The construction depends on the Axiom of Choice. But it is possible to construct paradoxical decompositions that do not involve Choice.... http://www.math.hmc.edu/funfacts/ffiles/30001.1-2-8.shtml If you are familiar with complex numbers, the "imaginary" number i has the property that the square of i is -1. It is a rather curious fact that i raised to the i-th power is actually a real number! ... http://www.math.hmc.edu/funfacts/ffiles/20013.3.shtml