Multiplication tables have some wonderful and quite surprising patterns. This is one of them. Draw any rectangle in a multiplication…

Pennies to Heaven is a Fermi Problem, basically a “headmath” experiment. Fermi Problems, originally developed by Enrico Fermi, one of…

Fractals are a new 21st century mathematics. They are patterns that repeat themselves at various scales. This one is based…

We take that great old problem of the inventor of chess and the ruler of India and use it to…

Scatterplot graphs enable us to build shapes using spreadsheets and to practice transformational geometry. They are surprisingly flexible tools. And…

Strings need not begin and end on axes that are at right angles to each other which we call Cartesian.…

Spreadsheets can be a great place for you to build your own games. Ryan has built one of his early…

How many of the numbers from 1 to 100 are in the times table? All, Most, Less than half? I…

Let's do a little target practice with this spreadsheet projectile simulator, which will map out the flight path of an…

Have you ever played Sudoku? It is fun and challenging. You have to find the numbers from 1 to 9…

Though spreadsheets lets you put geometric shapes on the screen, those shapes are not connected with the cells and cannot…

The usual way to make string diagrams using rubber bands or yarn on a board with nails does not allow…

What if you made a series of unit fractions with the odd numbers as their denominator, added the first two…