AustMS Gazette Puzzle Corner 25

The Australian Mathematical Society Gazette’s Puzzle Corner is a regular column with
entertaining mathematical puzzles, here’s an example: 

"Plugs and sockets 

Assume there are n types of power plugs and n types of power sockets in the world.  Each
plug type is compatible with exactly one socket type, and vice versa.  An adaptor
converts one socket type to another.  What is the minimum number of adaptors you would
need in order to connect any plug type to any socket type? Keep in mind that it is
possible to use multiple adaptors at the same time." 

You can find the Puzzle Corner, as well as the entire Gazette online at:
http://www.austms.org.au/Gazette+Volume+38+Number+5+November+2011 

Please check it out when you feel like trying out random fun problems, and be sure to
send your solutions in.  A $50 book voucher is up for grabs for the best submission, not
to mention fame, glory and eternal bragging rights! Entries are judged on the following
criteria, in decreasing order of importance: accuracy, elegance, difficulty, and the
number of correct solutions submitted.  

Please e-mail solutions to ivanguo1986@gmail.com or send paper entries to: Kevin White,
School of Mathematics and Statistics, University of South Australia, Mawson Lakes SA
5095 

The deadline for submission is 1 January 2012.  The solutions will appear in the May
2012 issue of the Gazette.  

Thank you

Ivan Guo 

P.S.  If you have nice mathematical puzzles, I would love to hear about them too.  They
may very well be featured in a future Puzzle Corner.