If you can read this clock, you are without a doubt a geek. Each hour is marked by a simple math problem. Solve it and solve the riddle of time. And if you don’t feel like doing the math, you can just memorize each problem’s position! It won’t take long to remember that the “52 – x^{2} + x = 10″ is in the 7 o’clock position. The Mathematics Blackboard Pop Quiz Clock makes a great gift for any math lover. You can purchase the clock here.