From Luzius Schneider:
Calcul will help your elementary school students practice mental arithmetic or to do fractions. Choose addition, subtraction, multiplication, division or fractions; then set the range of numbers and the number of calculations for an exercise. The program shows you two numbers or fractions respectively, and you enter an answer. Right or wrong answers get audio feedback and there's a pie chart to show your percentage of correct responses. For a greater challenge, play against a friend or set a time limit for a correct answer. The interface and sounds are available in English or German. More languages are supported.