## Work Time

# Make Quadrilaterals

Start with a sheet of paper. Fold the left edge toward the center at a slant. Then fold the right edge toward the center so that the right edge meets the left edge. Unfold.

Repeat the steps above using the top and bottom edges.

Look at the shaded center figure that is outlined by the folds.

- What type of figure is this? How do you know? Why do you think this type of figure was formed as a result of folding the paper the way you did?
- Measure each of the four angles inside the figure and write the measurements on the paper. What do you notice?
- For each of the four 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?
- What congruent angles do you see? What do these angles tell you about the figure?