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youcubed: Finding Pi  1. Construct a circle with a radius of 2 – 4 inches
2. Fold the circle into quarters and cut along the folds
3. Cut one of the quarters into eighths, two equal parts
4. Glue the pieces onto a piece of paper and draw the rectangle
5. The rectangle, ABCD has approximately the same area as the circle.
6. Calculate the area of rectangle ABCD
7. Construct another circle congruent to your first circle
8. Fold the circle into eighths, or eight equal sectors
9. Fit the circle pieces into a rectangle
10. Calculate the approximate are by determining the area of the rectangle.
11. Repeat the steps for a congruent circle cut into 16 sectors
12. AB is approximately half of the circumference, 2πr, why? This means AB = πr
13. Why does BC = r?
14. The area of rectangle ABCD is

Area ABCD = AB x BC = πr x r = πr²

## Materials

• Paper
• Compass/something to make a circle with a radius between 2 and 4 inches
• Scissors
• Glue

Geometry
K-6, Middle School, High School

## Organization

youcubed (Stanford University)

Challenge