Circles

Questions related to Circles are always on the GED math test.

This lesson is a part of Onsego GED Prep.

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1. Find the circumference of the circle if \(r =8\) ft.
Use this formula: \(C = 2\pi r\)
A.
B.
C.
D.

Question 1 of 2

2. Find the exact circumference of the circle if \(r=12\).

Use this formula: \(C = 2\pi r\)
A.
B.
C.
D.

Question 2 of 2


 

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Video Transcription

Today, we will explore how to find the radius or diameter of a circle and calculate its area and circumference.

The area of a circle is the space inside its boundary, and it’s calculated using this formula: Area = π × radius²
On the GED test, you are expected to use π = 3.14.

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The radius is the distance from the center of the circle to any point on its boundary.

Example: If a circle has a radius of 4 feet, its area is calculated as: 3.14 × 4² = 50.24 square feet.

The circumference is the total distance around the circle, and it’s calculated by: Circumference = 2 × π × radius

Example: For a circle with a radius of 4 feet, its circumference is: 2 × 3.14 × 4 = 25.12 feet.

Sometimes, a question gives the diameter instead of the radius. In that case, simply divide the diameter by 2 to find the radius.

On the GED test, you will usually get word problems, and you need to identify the necessary values to plug into the formula.

Here is a sample question:

A company designs various sizes of rotating garden sprinklers. The sprinkler head of model SPR-5 has a radius of 3 feet, meaning it sprays water in a circular area with that radius.

Using the formula for the area of a circle (provided on the formula sheet) and π = 3.14, what is the area of the circle covered by the sprinkler to the nearest hundredth?

Options:

  • A. 18.84 square feet
  • B. 28.26 square feet
  • C. 37.68 square feet
  • D. 40.72 square feet

Step-by-Step Explanation:

  1. Recall the formula for the area of a circle: The formula for the area of a circle is A = πr², where A is the area, r is the radius, and π is given as 3.14.
  2. Identify the radius: The radius of the sprinkler’s coverage is 3 feet.
  3. Plug the radius into the formula: Substitute r = 3 and π = 3.14 into the formula: A = 3.14 × (3)²Simplify:
    A = 3.14 × 9 = 28.26
  4. Interpret the result: The area of the circle covered by the sprinkler is 28.26 square feet.

Last Updated on January 15, 2026.