February 10–February 16, 2009

Problem

25 people go to a party on a cold winter day and leave their coats at the door. The first person to leave is in a rush and grabs one of the 25 coats at random. From there, as people leave, they either take their own coat if it is there, or grab a coat at random if their coat is not there.

What are the chances that the last person will take his own coat?

Solution

here

List of solvers

Alexander Isik (high school); Michael Draper, Matt Inouye (undergrad); Dustin Moody, Koopa Koo, Justin Shih, Peizhe Shi (graduate); Gary Raymond (staff); Peiyush Jain, Elizabeth McCranie, Hai Bin Chang, Steve Wilmarth, Roman Holenstein Mike Goodman, Vikas Hamine and Rajneesh Hegde, David Kaplan, Joshua Lim, Luan Nguyen, Lloyd Sakazaki (outside).

Peizhe Shi wins the prize!