Hungry Fish is a great free app that helps students practice mental math. Picture a fish floating around, needing to eat specific numbers or shrink and shrivel. The user must combine floating bubbles in order to make the specified sum. The free version allows the user to select low sums as well as sums up to 50. It's amazing how responsible students feel about feeding their fish! I have to admit that when I show students how to play, I become pretty sad when the fish keeps shrinking and darting around to look for "food." To increase their attachment to their fish, the program allows users to customize their fish with all different fins and colors. I have had students of all abilities really enjoy this app and improve their math skills. Without realizing it, they practice basic and more complex math facts. If I were teaching higher level math, I would definitely consider some of the upgrades since Motion Math has other applications that allow students to practice subtraction and negative integers. The high level of engagement and and free price tag make this app an easy decision! Enjoy!