Area and circumference of circles

6 videos
3 skills
You already know about area and perimeter of lots of shapes. Now we'll round out those concepts by applying them to circles. Mathematicians call the distance around a circle its circumference and the space inside a circle its area. In this tutorial, we'll learn that there's another type of pi in the math world, and it's even more awesome than apple pie. We'll use pi to find the circumference and area of any circle in the world, no matter how big or how small! Common Core Standards: 7.G.B.4

Circles: radius, diameter, circumference and Pi

VIDEO 11:05 minutes
A circle is at the foundation of geometry and how its parts relate to each other is both completely logical and a wonder.

Labeling parts of a circle

VIDEO 2:01 minutes
Radius, diameter, center, and circumference--all are parts of a circle. Let's go through each and make sure we understand how they are defined.

Area of a circle

VIDEO 4:02 minutes
In this example, we solve for the area of a circle when given the diameter. If you recall, the diameter is the length of a line that runs across the circle and through the center.

Area of a circle


Circumference of a circle

VIDEO 1:53 minutes
Here we find the circumference, the distance around a circle, given the area. We're building on our knowledge of the parts of circle.

Area of a shaded region

VIDEO 1:31 minutes
Here's a fun one: find the area of a shaded region where you first determine the area of a square and then the area of a circle.

Impact of a radius change on the area of a circle

VIDEO 3:31 minutes
If we change the radius of a circle, how does the circumference and area change?