We use the hundreds table to introduce rows and columns and focus students on seeing the patterns in these tables. Again and again we go back to making rules and using rules to ask and answer questions. For example, what rule would you make to fill in a column on the hundreds table. NOTE: we use color to connect a numbered task to a picture. You can remind students that they can change these colors if they want and copy and paste without changing a color by choosing Paste Formulas in the Paste Menu.
We have been using cell addresses informally until now, but now we can be more formal and explicit. Different spreadsheets have different types of address bars, but all use the same format, letters for columns and numbers for rows with letters first and numbers second. We introduce this on the hundreds table which could be thought of as a miniature spreadsheet and use number lines to provide some additional feedback. Using addressing enables us to build rules as patterns and to put anything we want into cells to use those rules on. It is the great power of spreadsheets.
Number Lines introduce students to functional thinking and the use of formulas in spreadsheets. For younger students we call these formulas “rules” and ask students to build a variety of number lines using rules. For example they can build a whole number line by creating a rule that adds 1 to the number in the previous cell (=J9+1) and then copy that rule across the numberline cells. They build numberlines with only odd numbers, even numbers, and starting with different numbers. We encourage them to explore a variety of rules to make different numberlines.
1, 3, 6, 10… are called the triangular numbers because they can be stacked up to form a triangle. They are very interesting numbers, and they form a very interesting pattern when graphed.
Can you guess the next triangular number? Can you guess the shape of the graph of the triangular numbers? Can you explain that graph?
Spreadsheets are great for creating secret codes and for breaking them. During World War II the German military used a machine they called Enigma to send coded messages. In a box about the size of a typewriter, wheels with letters on them were spun around to encode or to decode a message. The story of the breaking of that code by Alan Turing and the British code breakers was made into the movie The Imitation Game. We have used spreadsheets with some of their built-in rules to let you set up your own enigma machine. There are many ways you can use a spreadsheet to generate or to crack codes. It is fun to see if you can make a code your friends can’t break.