A cheerful slide rule with which children can 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 allows them to playfully practice with a cheerful slide rule.
