Terrific Triangles for Mac

From Elementary Software:

There are 2 playing modes. In all cases the triangle presents two parts of a fact family and the player must determine the missing third part. The sum and product always appear at the top of the triangle. The addends and factors always go in the two lower corners. Student mode allows individual facts practice with a running score for correct answers. The player may select difficulty and whether to play against a timer. Teacher mode allows for group play. Students are presented with a problem and the timer spins one revolution. Then a student name appears and the timer spins again. The student who's name is shown tries to call out the answer before the timer finishes. We like this system of showing the student name after the first spin because, if the time is set short enough, students are encouraged to pay attention even before knowing whether they will need to answer. If they wait until they see their name (or a neighbor tells them to look!) it may be too late to calculate. Press the "Return" or "Enter" key for a new problem to display. The empty corner will be random. If you wish to select which corner will be blank, click that corner with the mouse instead of using the keyboard. Student mode may be used right away. Generally teacher mode requires that names be entered first. The names and settings will remain saved between uses.