This app is developed for and together with children who are learning the first steps in calculating with decimals. This app explains in 10 steps how to calculate with decimals. The app contains ten chapters with several instruction pages and in total 26 interactive exercises as well three quizzes. A booklet, which children use at school, is the idea on which we based this app. This app is perfect for training tests at school and to exercise at home or school difficult subjects regarding calculating with decimals.