# Time to Kill: Fire!

The PSAT gave one class period a bonus day. I like to have a few things up my sleeve for these kind of days. Building stuff out of straws is fun. So is the Chaos Game. This time I went with an activity I remember from 6th grade. I don't remember much about what we learned in 6th grade, but we did a couple things with probability. One is the classic Game of Life the other is Forest Fires.

Materials: dice, blank forests (PDF)

The forest is generated randomly using a six sided die. Place your finger on a square. Roll the die. If the number rolled corresponds to "tree" for the forest card you have, mark the square with a colored dot. If the number rolled corresponds to "blank" move on to the next square.  27 kids rolling dice is LOUD.

Each student got two cards. It took 15-20 minutes for them to generate the forests. To provide a visual for the intended output, I rigged up some conditional formatting and random number generation in Excel:

Next, light the thing on fire, so to speak. Announce that every "tree" square on the left is now on fire. The fire will spread if there is a tree to the right of the new on fire square. From there, fire spreads to trees up, down, left, or right of a lit square. Fire does not spread diagonally. At the end, they counted the number of trees that survived. I passed out awards for most trees standing and most trees killed. The probability of "tree" on some cards was so high that one student burned down every tree on the card.

If probability is part of your curriculum, or you teach 6th grade, you can use this activity to generate some extensions. For me, it filled the extra day perfectly.

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