## Tree House Lesson (w/ Most Nifty Part)

So, I survived the first week of my summer program.

It’s called an Algebra Academy and it is for incoming 9th graders. (They still act like 8th graders.) It’s a mixture of mathematics, science, and engineering, culminating in a contest with several other schools using bottle rockets.

Today’s lesson I didn’t write myself, but it included a part that kicked everything up a notch, so I wanted to share.

Note that as run this lesson was more an engineering/design lesson, fairly light on the math, but it would be easy to ratchet up the geometry.

Building a Tree House

Materials needed: Popsicle sticks (about 1000 for a large class), toothpicks (300-400 ought to do), tissue paper (substitute other colored paper type as needed), string, glue sticks (lots), scissors. (Also found out post-lesson sandpaper would have been handy.)

So, we told the students they were building a tree house with these restrictions: it needed a ladder to get up the tree, some sort of roof for shelter from weather, and given a 1 foot = 1 inch scale it had to hold at least 3 people.

They designed their tree house first using isometric paper, and they had to work out beforehand how much supplies they needed.

Then they “bought” their supplies. We kept expense accounts. We had

Popsicle sticks (aka large boards): \$3 each
Toothpicks (aka small boards): 50 cents each
String (aka rope): 25 cents an inch
Colored paper (aka gallons of paint): \$6 each
Glue sticks (aka nails): free

After the initial buying stage — here’s where the twist came in — all the prices doubled. We warned the students beforehand prices would go up after they got back from their break, but they all still boggled at the new price board.

This made the whole affair like a strategy game. First off it forced the students to plan well, and a couple even tried to use their math skills to help. Then students had a choice: do I buy what might be too much and risk wasted materials and money, or do I risk hitting the exact right amount when a shortfall could mean a much higher expense?

After it was all over, we judged. Cost came into play, but also design, stability, and practical ability to be used as a tree house.

Unfortunately I won’t be able to get any pictures. For some reason the students were keen on wrecking their creations after the whole thing was done. One tree house was intensely stable so they did an impromptu experiment of “how many textbooks can we stack on top before it collapses?” It lasted for 25 before it went down.