Looking for an interesting mathematical challenge? Try your hand (brain) at the current challenge problems from the USA Mathematical Talent Search (USAMTS). These are some great problems — they are interesting while still being accessible to most high school mathematics students. The idea behind the USAMTS competition is to encourage creative problem-solving. You can sign up for free and submit your solutions (you have to write an explanation of your solution, not just a number) and a grader will actually score your solutions and offer comments. Fun math problems, with feedback, for free — what’s not to like? Solutions for the current set of problems are due in early October, when the next set of questions comes out.