The Australian Mathematical Society Gazettes Puzzle Corner is a regular column with entertaining mathematical puzzles, heres 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 firstname.lastname@example.org 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.