## Circle Tool

Grade:

3-5, 6-8

Standards:

Math Content:

Geometry

How do the area and circumference of a circle
compare to its radius and diameter? This activity allows you to investigate
these relationships in the Intro and Investigation sections and then hone your
skills in the Problems section.

### Modes

- In the
**Intro**section, explore the relationship of the circumference to the radius and diameter. Play the movie clip to visually see how they are related. - In the
**Investigation**section, collect data points by dragging the radius to various lengths, and the click the "Add to Table" button to record the data in the table. By default, the radius, diameter, circumference and area are shown in a table.- Clicking on the
**x/y**button allows you to examine the relationship between any two measures. - Clicking on the
**graph**button will take you to a graph of the data. You can plot any of the four measures on the*x*-axis against any of the four measures on the*y*-axis.

- Clicking on the
- In the
**Problems**section, determine the answer to each question using the applet, a calculator, or paper and pencil. Don't forget to indicate the proper units!

Can you determine the relationship between…

- …radius and diameter?
- …radius and circumference?
- …diameter and circumference?
- …radius and area?

Some relationships can be discovered using the **x/y** button. Others will
require more investigation, but the graph should give you some insight.