One of those games is called Corners. This game is used to help children add or subtract by 5,10, 15 and 20. The object is to match up one of the sides of your cards to another card in the playing area that fills two requirements:
- The numbers have to be the same color.
- The sum of the two numbers must equal 5, 10, 15 or 20.
Here is Biggest playing against me one day a few months ago. She uses the abacus when she has trouble adding the numbers in her head. She has since gotten much better at this and doesn't use the abacus near as much.