The Lesson

The area of a one is discovered using the formula:
In this formula, d is the diameter that the circle. The image listed below shows what we typical by diameter:

Interactive Widget

Use this interaction widget
to draw a circle and then calculate its area indigenous the diameter. Start by click in the shaded area.

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How to find the Area that a Circle using the Diameter

Finding the area the a circle making use of the diameter is easy.


What is the area that a circle with a diameter the 10 cm, as presented below?

Area = π × 102⁄4

Area = π × 10 × 10 ÷ 4

Area = π × 100 ÷ 4

Area = π × 25

Area = 3.14 × 25

Area = 78.5 cm2

Lesson Slides

The slider below shows another real example of exactly how to uncover the area the a circle making use of the diameter.Open the slider in a new tab

How to find the Area the a Circle making use of the Radius

The area of a circle deserve to be discovered using the radius fairly than the diameter.The area that a circle, making use of the radius, is found using the formula:
In the formula, r is the radius that the circle. The image listed below shows what we median by radius:
Read an ext about just how to discover the area the a circle making use of the radius

What Is a Circle?

A circle is a form containing a set of clues that room all the exact same distance from a offered point, its center.

Why go This Formula Work?

The formula for the area the a one is much better known in terms of the radius:
The radius have the right to be uncovered from the diameter. The radius is fifty percent the size of the diameter:
Substitute d⁄2 because that r:
The d⁄2 in the base is being squared. When a fraction is squared, both the numerator and also the denominator room squared:
This is is formula because that the area of a circle making use of the diameter.

A keep in mind on Units

The area that a circle is a length times a length, so us say its measurement is length2. (All locations are lengths squared).This affects the devices used. If the diameter is in cm, the area is in cm2. If the is in inches, the area is in inches2.

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See Also

What is a circle?What is pi?What is the diameter?Find the area of a circle using the radiusHow to discover the radius indigenous the diameterThe exponent where the basic is a fractionWhat is the numerator?What is the denominator?

The Test

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