# Introducing Subtraction

What if you built a rule that would enable you to count backwards? How would it be the opposite of addition? What would happen if it goes past zero?

# Make a Hundreds Table

This is the graduation exercise for the basic use of spreadsheets. We combine rules and addressing to have students build their own hundreds table in the fewest steps. There are many ways of doing this and students can be as creative and exploratory as they want. Nor should they feel limited to tables that start at 1 and go to 100. These rules, these patterns should enable them to start anywhere and build any size table they can imagine. We strongly encourage students to stretch their minds here and to think outside of this box.

# Sudoku Challenge

Have you ever played Sudoku? It is fun and challenging. You have to find the numbers from 1 to 9 in each cell so that that all of the numbers appear only once in every row, column, and grid square. Ryan added a sweet wrinkle to the traditional Sudoku game, he gives you the sums so that you not only get to practice addition, you can get some hints about the numbers you should input. Can you use our template to create your own Sudoku challenge?

# Subtraction Tables

What would a subtraction table look like? How would its pattern be different from an addition or multiplication table? Is subtraction commutative?

# Number Patterns

Use numberlines and spreadsheet rules to explore the amazing patterns we find in our whole numbers. Did you know that you can get the odd numbers by subtracting the square numbers? I won’t give away any other secrets, but I know you will find in these patterns some wonders. And you may even construct your own numberline patterns that no one has ever seen before.