The abacus has 5 red and 5 white beads with which you can practise the structures of ten, five and double numbers. With these structures, number pictures can be created that enable you to automate adding and subtracting of numbers up to 20. You can choose between 20 or 100 beads.
Slide one or multiple beads from right to left. Or slide them from left to right. Click on 'Reset' and all the beads will be shown on the right hand side.