# Create a Gum-drop dome

[dropcap1]W[/dropcap1]ith just a few gumdrops and some toothpicks you can build some pretty cool structures that are amazingly strong yet simple in design.

**What you need:**

- Box of Toothpicks
- Bag of Gumdrops

** What to do:**

- Use gumdrops to connect 5 toothpicks in a ring. This is your base.
- Use 2 toothpicks and 1 gumdrop to make a triangle on one side of the base.
- Repeat all the way around the base until you have 5 triangles.
- Use toothpicks to connect the gumdrops at the tops of the triangles. Now how many triangles do you have?
- Push 1 toothpick into each of the top gumdrops.
- Use one last gumdrop to connect these toothpicks at the top.

** What’s the science?**

Engineers often use triangles when they design buildings. Did you notice that your dome is made up of lots of triangles? That’s because triangles are stable shapes. That means they don’t bend, twist, or collapse easily when you push on them. A square is not as stable as a triangle. Test it. Make a square and a triangle out of toothpicks and gumdrops. Press down on one corner of each shape. How do the two shapes compare? Does one bend, twist or collapse more easily than the other?

** What will happen if . . .**

- you make a base with six sides instead of five sides?
- you build squares rather than triangles on top of the base?

Choose one thing to change (that’s the variable), and predict what you think will happen, then test it.

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