Thursday, February 4, 2010

Pascal in Excel

As an enrichment activity I had a student fill a large sheet of graph paper with Pascal's triangle - just the ones digits, anyway.  Then he colored the digits in different ways to discover patterns.  After doing this by hand, the student was interested in saving some time with Excel, so I devised this method:

  1. Make a grid of 0's.  Really you just need a border of 0's, but filling an area is faster.  It should be twice as wide as tall.

  2. Select cell B2, and give it the formula =MOD(A1+c1,10).
    pascalexcel1

  3. Copy B2 and paste it into all the cells in the grid except for the top row and the left and right columns.

  4. Now they are all adding the values of the two cells diagonally above them.  Just put a "1" in the middle of the top row and see what happens.
    pascalexcel2

  5. To color the different digits, click Format, Conditional Formatting, and make some stuff up.
    pascalexcel3

  6. I changed the font color to white and clicked File > Web Page Preview:
    pascalexcel4


You could do some fun experiments with this, leading kids toward the idea of cellular automata!

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