## Frank Morgan's Math Chat |

December 17, 1998

ANSWER. In a tight race between 7 and p, p wins by a single vote. (p is what you get when you divide the circumference of any circle by its diameter.) Sebastian Zwicknagl reasons that all integers are equally interesting, but that p is special. Arthur Pasternak realizes that an internet audience might choose the more mathematical number. And as Dean Thomas puts it, "p is the most mathematical number I know!" Joel Foisy calls it "the best known irrational number." Rational numbers have decimal expansions that either end or repeat, such as 1/4 = .25 or 1/3 = .333..., but

goes on forever. Amazingly enough, p comes up not only in geometry, but in almost every branch of mathematics.

Other contenders include 0, 1, 2, 17, and 70.

**NEW CHALLENGE** (Steve Jabloner). How many times do you think you need to
role a normal die to be 90-percent sure that each of the six faces has
appeared at least once? Why?

Copyright 1998 Frank Morgan

Send answers, comments, and new questions by email to
Frank.Morgan@williams.edu, to be eligible for *Flatland* and other book
awards. Winning answers will appear in the next Math Chat. Math Chat
appears on the first and third Thursdays of each month. Prof. Morgan's
homepage is at www.williams.edu/Mathematics/fmorgan.