This is a free version of "Interactive Matrices PRO", if you want the ad free version search in the android store for "Interactive Matrices PRO".
This app and matrix calculator is ideal for students and graduates, you will find a variety of useful tools for matrix calculus and you can enter a value by touch, the interactive feature make it easy to avoid typing or human errors.
The interface is made in a way that you can see above any variable it's value.