Finding the Circumference of a Circle

Who wants PIE??

 

Hands-on activities are the best ,especially for teaching math! I feel its important to not just teach the students the formula but rather teach the depth of knowledge that common core expects. If I were to teaching a sixth grade class on how to find the circumference of the circle, this is what it would look like:

First, I would place students in groups of five, but each student has their own set of supplies (math kit). I want them each to experience the activity, but I also want them to be able to ask questions amongst each other and compare their measurements. This helps students to realize that they can figure things out amongst each other and not rely solely on me.

Direct students to as-close-as-they-can place one end of the string on the edge of the circle and outline the circle with the rest of the string. Make sure students only go around the circle once. Here is a picture of what it should look like.

 

I would tell them to pinch the part of the string that touches the loose end on the circle. Make sure they understand that they are putting the string around the circle in order to “measure” the distance around the circle. You can’t measure it with a ruler because it is straight and the circle is round. Then I would have them measure the string using a ruler (cm).

Then, I would have them record the circumference on the chart such as the one listed below. Then, they would do the same steps for finding the diameter.

Once the students have found the circumference and diameter for each object, I would have them look at the relationship between them. This part of the lesson will simply be student centered ,where the students are discovering the relationship on their own. The idea behind it is that the circumference divided by the diameter would give you a estimate of 3.14 or in other words, pi.

As a result of this lesson, students will be able to understand the relationship between the circumference, diameter and pi. They will also discover the formula for the finding the circumference of a circle, which is:

C= π x d    (Circumference equals pi multiply by the diameter)

 

 Check out the SHOWME video link below.  I have completed for reteaching, absent students or simply students who need a refresher! ;)

How to find the circumference of a circle