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# Geometry for Nursing School Entrance Exam Study Guide (page 6)

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Updated on Aug 12, 2011

### Area

The area of a circle is the space its surface occupies. To determine the area of a circle, use this formula:

Hint: To avoid confusing the area and circumference formulas, just remember that area is always measured in square units, like 12 square yards of carpeting. Thus, the area formula is the one with the squared term in it.

Example: Find the area of the circle at right, rounded to the nearest tenth:

1. Write the area formula:
2. Substitute 2.3 for the radius:
3. On a multiple-choice test, look at the answer choices to determine whether to use π or an approximate value of π (decimal or fraction) in the formula. If the answers don't include π, use 3.14 for π (because the radius is a decimal):
4. If the answers include π, multiply and round:

Both answers—16.6 square inches and 5.3π square inches—are correct.

Example: What is the diameter of a circle with an area of 9π square centimeters?

1. Draw a circle with its diameter (to help you remember that the question asks for the diameter); then write the area formula:
2. Substitute 9π for the area and solve the equation:

Since the radius is 3 centimeters, the diameter is 6 centimeters.

The practice quiz for this study guide can be found at: