Ive been looking for such an app like this but found it hard to find a good/perfect one despite the simplicity of the logic that goes in the app. I wish there would be more difficult levels with lengthier numbers, however. Perhaps little more options to tweak the arithmetic questions would be nice. For ex. Questions such as 2M / 200 = (20K) would be useful for ppl like analysts(like me). Anyways, great app! I payed for this app w/ no hesitation.