## Circle Tool

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.

• 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…