Exploring Circumference

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SWBAT explore a relationship between diameter and circumference of a circle.

Big Idea

How does the diameter compare to the circumference of a circle?


30 minutes

The exploration has several steps, including cutting and measuring. To ensure that students have enough time to finish the activity, we will not do a POD today.

To explore the relationship between the diameter and the circumference of a circle, students will measure the diameter and circumference of several circles. The sheet, Exploring CIrcumference, will be used to organize the data students generate. Students will receive between 2-4 circles and yarn and scissors.  They will find the length of the circumference using the yarn for each circle. They will also measure the diameter of each circle and record the information on the data sheet. Once the data sheet is complete, students will review it to see if they recognize any patterns between the diameter and the circumference. They should complete the chart and other information on the data sheet. I want them to see that the circumference is “about” three times the diameter. After the recognition, we will work to develop a formula for finding the circumference. Do they recognize that pi is about 3? Are they familiar with pi? They will calculate the circumference for each other circles measured and discuss any observations and conclusions as a whole group.


5 minutes

To exit the class, I want students to sum up their thinking on circumference and how to find the circumference of any circle. How will they remember and apply a formula to find circumference? Do they have a “way” to remember or are they memorizing a formula and don’t yet understand, conceptually, what the formula represents? I wanted to leave the prompt a little vague to find out exactly what students think.

Tell me how to find the circumference of a circle. What does that mean?