Would not recommend...

...this app to be purchased to help with math. It is basically just teaches shortcuts to learn difficult math problems. This app gives students a procedural understanding for how to do certain math problems. Although certain math procedures may be used to solve the difficult math problems, these are all just short cuts. By having the student learn to actually solve the difficult problem would be much more beneficial for the student because it will help the student develop a conceptual understanding instead of just learning a shortcut to solve the problem. Only way this app could be beneficial is to get students to think about why these certain shortcuts work. But they would need to have a conceptual understanding of how to solve the problem on their own before they could do that.

Jonze about Mathemagics: Mental Math, v5.0.1