The departments of Mathematics, Applied Mathematics, and Statistics at the University of Washington present the

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01/27/2009
01/20/2009
01/13/2009
01/06/2009
12/02/2008
11/25/2008
11/18/2008
11/11/2008
11/04/2008
10/28/2008
10/21/2008
10/14/2008
10/07/2008
09/30/2008
09/23/2008
09/09/2008
08/26/2008
08/19/2008
08/12/2008
08/05/2008
07/29/2008
07/22/2008
07/15/2008
07/08/2008
07/01/2008
06/24/2008
06/10/2008
06/03/2008
05/27/2008
05/20/2008
05/13/2008
05/06/2008
04/29/2008
04/22/2008
04/15/2008
04/08/2008
04/01/2008
03/18/2008
03/11/2008
03/04/2008
02/26/2008
02/19/2008
02/12/2008
02/05/2008
01/29/2008
01/22/2008
01/15/2008
01/08/2008
12/04/2007
11/27/2007
11/20/2007
11/13/2007
11/06/2007
10/30/2007
10/16/2007

March 4–March 10, 2008

Problem

Suppose that each of n people knows exactly one piece of information, and all n pieces are different. Every time person "A" phones person "B", "A" tells "B" everything he knows, while "B" tells "A" nothing. What is the minimum number of phone calls between pairs of people needed for everyone to know everything?

Solution

here.

List of solvers

Todd Freed, Dan Siddoway (undergrad), Gary Raymond, Steve Wilmarth, Dustin Moody (graduate), Mike Goodman, Lloyd Sakazaki, Stefan Sharkansky, Eric Brodeur (outside).

Lloyd Sakazaki wins the prize this week!