Set of 4 cheerful slide rules that allow children to practice number bonds up to 10: When the window is set to 10, you can read all the number bonds of 10 to its right, from top to bottom: 9 and 1, 8 and 2, etc.
When you set the window to a different number, you will see all its number bonds to the right.
This way, they can playfully practice with a cheerful slide rule.
