Arithmetic and calculus trainers

I want to train my mental arithmetic and calculus skills. Do you know of any games or libraries that can generate questions up to freshman level calculus? (Preferably Scheme or Haskell)

>>3
(A) if a/b is a repeating decimal so is 10a/b.
(B) if a/b is an integer it is not a repeating decimal.
(C) (by A and B) if 10^k a/b is an integer for some k, then a/b is not a repeating decimal
(D) (by the contrapositive of C) if 10^k a/b is not an integer for any k, then a/b is a repeating decimal