Discovering Pi
Step 1: Each person pick a circle and a cookie to measure from your table (so make sure each group
member has 2 circles to measure).
Step 2: To measure around, use the string provided. Wrap around the outside edge and then measure
the distance with a ruler. Record this measurement in the table.
Step 3: To measure across the middle, locate the center of the circle, then use a ruler to measure the
distance from one side of the circle, through the center, to the other side of the circle. Record this
measure in the table.
Step 4: Record your the other objects' measures in your table.
Step 5: Use a calculator to divide the circumference by the diameter. Record your measure in the
table.
Distance Around the
Distance Across the Circumference Divided
Object
Middle of Object
By Diameter
Object
(Circumference) to the
(Diameter) to the
to the nearest onenearest tenth of a
nearest tenth of a
hundredth of a
centimeter
centimeter
centimeter
Cookie
Mean from above:
Answer using complete sentences.
1. What do you notice about the numbers in the last column?
2. Can you come up with a conclusion about the values in the last column? (this is not a yes or no
answer)
Formula for the estimate of Pi:
Use the Pi formula to solve for circumference of a circle:
Use the Pi formula to solve for the area of a circle:
Circumference and Area Problems.
1. A circle has a radius of 4 cm. Show the correct formula and solve to find the circumference of
that circle.
2. A circle has a diameter of 10 inches. Show the correct formula and solve to find the area of that
circle.
3. The circumference of a circle is 18.84 cm. Show the correct formula and solve to find the radius of
the circle. What is the diameter of the circle?