A free app for Android, by Visual Math Interactive.

4th Grade Math: Fun Kids Games is a learning app that helps kids in 4th grade learn common core math in a fun and interactive way. The lessons are designed to help kids understand and master the concepts of factor pairs, figure out number patterns, relate place value with multiplication and division, round numbers, find equivalent fractions, understand decimal notation for fractions, represent and interpret data, understand and measure angles, draw and identify lines and angles, and classify shapes by their lines and angles.

You can also earn achievements as you progress through the game. These can be collected on your device or on the web, and they can be tracked on the website.