I'm thinking about 12th grade, if you take calculus.
To follow Josh's post, maybe 11th grade.

note that there are different levels of difficulty at perplexus (1-5); and this problem is level 4.  Don't be discouraged, browse or search through old problems.

Edited on August 13, 2005, 5:30 am

Posted by Larry on 2005-08-13 05:28:06