Aust MS Gazette - Puzzle Corner 21

The Australian Mathematical Society Gazette’s Puzzle Corner is a bimonthly column
containing a handful of entertaining mathematical puzzles.  The puzzles cover a range of
difficulties, come from a variety of topics, and require a minimum of mathematical
prerequisites to be solved.  

You can find the Puzzle Corner, as well as the rest of the Gazette online at:
http://www.austms.org.au/Gazette+Volume+38+Number+1+March+2011 

Please check it out when you feel like trying out random fun problems! Should you happen
to solve any, be sure to send your solution to us.  In each Puzzle Corner, the reader
with the best submission will receive a book voucher to the value of $50, not to mention
fame, glory and unlimited 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 of solutions for Puzzle Corner 21 is 1 May 2011.  The
solutions to Puzzle Corner 21 will appear in Puzzle Corner 23 in the July 2011 issue of
the Gazette.  

Thank you! 

Ivan