Lesson Sample: Area of a Circle

We are currently developing the online version of our math curriculum. Here is a sample lesson:

Finding the area of a circle

areadiagramA circle is a collection of points a certain distance (its radius) from another point, its center. The area of the circle is all of the space inside of it.

To find the area:

  1. Take the radius (r) of a circle (the distance from the circle’s center to any point on the circle itself)
  2. Square it
  3. Multiply by π (the Greek letter pi, pronounced “pie,” is an irrational number that’s a bit more than 3: round pi to 3.14 or 22/7)
  4. That gives you the circle’s area (all of the blue space inside of it).

The formula for these steps: π r 2 = A

  • r is the radius of the circle
  • A is the area of the circle
Note that squaring a length (like a radius) turns one-dimensional space (something you can measure with a ruler, like a radius) into two dimensional space (the area of the circle).

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