AustMS Gazette Puzzle Corner 28

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

"Mean marks 

The final exam marks have just been released.  Within each class, the boys have a higher
average score than the girls.  Does that necessarily mean the boys have a higher average
score across the entire grade?" 

You can find the Puzzle Corner, as well as the entire Gazette online at:
http://www.austms.org.au/Gazette+Volume+39+Number+3+July+2012 

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.  

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 30 September 2012.  The solutions will appear in the
November 2012 issue of the Gazette.  

Thank you 

Ivan Guo