Mental Math Trainer for iPhone

I made this app because I wanted to practice my math and I was tired of downloading other apps that only allow you practice problems that you could do in your sleep. This app allows you the freedom to choose the difficulty of the math you want to practice, not by arbitrary ratings, but by the number of digits used in your operations. Problems with up to 9 digits can be done (5 for multiplication due to architecture limitations)Now package up that freedom with a beautiful interface and I'd say download this app and go practice your math!