1. For this activity, I design these stackable, concentric circles.
7” diameter
6” diameter
5” diameter
3/8” center cutout
4” diameter
3” diameter
For this activity, I design these stackable, concentric circles.
A local cabinetmaker made 6 sets for my classroom. You can use round household objects, too.
at least 3/4” height
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

2. Find a group of 4. Each group needs: 1. piece of graph paper
2. set of concentric circles
3. painter’s tape
4. meter stick
5. scissors
6. markers
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

3. red orange yellow green blue
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

4. red orange yellow green blue 7.6 cm 10.2 cm 12.7 cm 15.2 cm 17.8 cm
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

5. circumference diameter
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

6. (0,0) There will not be a circumference relationship between C & d
without a diameter.
m ≈ 3.08
relationship between C & d
= 0.06
y = Cx d
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

7. rise (y-values) over run (x-values)
C = 2πr = π
d r
Circumference
diameter
rise (y-values) over run (x-values)
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)

8. Summary Questions What does it mean to say that π is a ratio?
Does the ratio of circumference to diameter vary depending on the size of the circle or the unit of measurement (in., cm)? Explain.
© 2009, Dr. Jennifer L. Bell, LaGrange High School, LaGrange, Georgia (MCC9-12.G.GMD.1)