1. Circumference of a Circle
Geometry
Oct 28, 2013

2. Distance around circumference Perimeter A Polygon is known as the
The outside of a circle is known as the
Perimeter
circumference

3. Your Tasks…
1. Measure the “distance around” and the “distance across” of the objects.
Distance across – be careful when identifying the exact middle of an object.
Distance around – To ensure accuracy, care should be taken to keep the string taut when measuring the outside of a circular object.
2. Use the same unit of measure (inches or centimeters) for distance around and distance across.

4. Apple Pi activity sheet.
Record the following information
1. Description of each object
2. Distance around the outside of each object
3. Distance across the middle of each object
4. Distance around divided by distance across
(use your calculators for this part)

5. Discuss The average and note any interesting findings
Compare your averages with those of other groups

6. Findings 2r 𝑷𝒊 ≈𝟑.𝟏𝟒… 𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 = 𝜋
The ratio you just found is known as
Distance across = Diameter
Distance around = Circumference
𝑷𝒊 ≈𝟑.𝟏𝟒…
𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 = 𝜋 2r
𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒= 𝜋∙𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟
𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒=2𝜋𝑟

7. Questions to write about..
Why did we use the ratio of circumference to diameter of several objects? Wouldn’t we have gotten the same result using just one object?
Were any of the ratios in the last column not close to 3.14? If not, explain what might have happened
Describe some situations in which knowing the circumference (and how to calculate it) would be useful.

8. Homework… Circumference and Area worksheet # 9 – 20, 25, 26
Also, refer to the helpful videos in my website

9. Tomorrow…
Please bring
1. Several FLAT CIRCULAR objects
2. Scissors