## Build Triangles

## Work Time

# Build Triangles

Start with a sheet of paper. Fold the left edge toward the center at a slant. Unfold. Fold the right edge toward the center so that the fold overlaps the first fold you made. Unfold. Fold the bottom edge toward the center so that the fold overlaps the first two folds you made. Unfold.

Look at the figure that is outlined by the folds.

- What type of figure is this? How do you know? Why do you think this figure was formed as a result of folding the paper the way you did?
- Measure each of the three angles inside the figure and write the measurements on the paper. What do you notice?
- For each of the three angles you measured, there are three angles that share the same vertex but lie outside the figure. What is the sum of these three angles? How do you know?

## Hint:

- What is the sum of the angles in your triangle?
- Check with other students nearby. What is the angle sum in their triangles?