## Learning Math: Geometry

# Triangles and Quadrilaterals Part C: Building Towers (45 minutes)

## Session 2, Part C

In Part C, you will apply what you’ve learned about the properties of figures to a construction task.

**Problem C1**

Gather toothpicks and mini marshmallows, or other connectors. Your job is to work for 10 minutes to build the largest freestanding structure you can. “Freestanding” means the structure cannot lean against anything else to keep it up. At the end of 10 minutes, stop building, and measure your structure. **Note 5**

**Problem C2**

What kinds of shapes did you use in your structure? Which shapes made the building stronger? Which shapes made the building weaker?

**Problem C3**

If you had the chance to build the structure again, what would you do differently?

**Problem C4**

Get another set of building materials and take an additional 10 minutes to create a new freestanding structure. Your goal this time is to build a structure taller than the one you made before.

Building Towers problem adapted from IMPACT Mathematics Course, 2, developed by Educational Development Center, Inc. pp. 476-477. © 2000 Glencoe/McGraw-Hill. Used with permission. www.glencoe.com/sec/math

### Note 5

If you are working in groups to build your structures, at the end of 10 minutes, measure your structure, and then compare the structures built by the different groups. Consider the following questions:

- For the tallest structures in the room, what kinds of strategies did the creators use?
- What kinds of structures had trouble standing up? Which ones were stronger?
- What kinds of shapes were stronger in keeping the buildings up? Can you explain why?

### Solutions

**Problem C1**

Constructions will vary.

**Problem C2**

Answers will vary depending on the construction, but in general, structures whose surfaces are defined by quadrilaterals will be less sturdy than those whose surfaces are defined by triangles.

**Problem C3**

Answers may vary, but as we’ve learned, triangles are more rigid than quadrilaterals. Similarly, using a wide base and building “up” with triangles is the best approach. Builders find that if you want a square- or rectangular-shaped building, you must build triangular supports into the “walls.”

**Problem C4**

Constructions will vary.