Mental Math Practice is a free Android app offered by Magoosh, an online test preparation company. With this app, you can master mental math with a collection of 200 flashcards that cover different types of math practice. These flashcards are crafted by an expert math tutor and include explanations of shortcuts for every arithmetic calculation, including addition, subtraction, multiplication, division, and more.

The app also offers decks for different types of math practice, including 2-digit and 3-digit addition and subtraction, multiplication, division, doubling and halving, fractions, decimals, and percents. You can track your progress as you study and the smart algorithm focuses your math practice for efficient learning. The app uses a spaced repetition system that allows you to review the concepts you're learning frequently, while those you already know won't be repeated.