How to Find the Radius of a Circle: Definition & Formula


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question 1 of 3

If the diameter of a circle is 10, what is the length of a radius of that circle?

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1. If the circumference of a circle is 12 centimeters, what is the radius of the circle?

2. You know the area of a pizza pie is 154 square inches. What is the radius of that pizza pie?

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About This Quiz & Worksheet

This quiz and corresponding worksheet will help you gauge your knowledge of finding the radius of a circle. Topics you'll need to know to pass the quiz include understanding the method to calculate the length of the radius of a given circle.

Quiz & Worksheet Goals

Use this printable worksheet and quiz to review:

  • Solving for radius given circumference or diameter
  • Determining radius when given the area
  • Identifying how a minute hand of a clock could be described

Skills Practiced

This worksheet and quiz will let you practice the following skills:

  • Defining key concepts - ensure that you can define main concepts, such as diameter, circumference, and radius
  • Knowledge application - use your knowledge to answer questions about the radius of a circle
  • Problem solving - use acquired knowledge to solve for the radius

Additional Learning

To learn more about how to calculate half the length of a circle, review the corresponding lesson titled, How to Find the Radius of a Circle: Definition & Formula. This lesson will help you:

  • Define what the radius of a circle is
  • Understand how the radius relates to the circumference
  • Show the process to get the diameter from the radius
  • Identify the formula to calculate a circle's area
  • Describe what radii in real life could look like
  • Appreciate how to solve for the radius of any circle