Problem of the Week

In this space, I will try to post an interesting and challenging puzzle or short problem every week. I am giving these problems to my classes for their mathematical entertainment. Some of the weekly puzzles I invented myself, but many are scavenged from other sources. If you would like to contribute a problem, please email me. Enjoy!

Second Week, January 17. The Circular Lake.

You are in a boat on a perfectly circular lake. A hungry, evil goblin is waiting for you on the shore and wants to eat you. The goblin cannot swim, but he can run four times faster than you can row. If you could reach the shore without meeting the goblin, you would be saved, because you can run faster than the goblin. Can you get away? (after M. Gardner, Mathematical Carnival.)

Clarifications: 1) In the beginning, you are at the center of the lake. 2) You may not assume anything about the strategy of the goblin. The goblin could be very smart.

Note: I am not giving out solutions to "Problems of the Week". But I am very happy to discuss these problems with you, including any partial or attempted solutions that you might have. I am always interested in hearing about interesting or creative solutions, so let me know if you have any!

See previous Problems of the Week.

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Peter Selinger / Department of Mathematics and Statistics / Dalhousie University
selinger@mathstat.dal.ca / PGP key
Updated Jan 17, 2000