What Is the Circumference When You Know the Area Formala
A circle is a shape with all points the aforementioned distance from the centre. It is named by the heart. The circle to the left is called circle A since the center is at point A. If you measure the distance effectually a circumvolve and dissever it past the distance beyond the circle through the eye, you will e'er come shut to a particular value, depending upon the accuracy of your measurement. This value is approximately 3.14159265358979323846... Nosotros apply the Greek letter of the alphabet
(pronounced Pi) to represent this value. The number goes on forever. Withal, using computers, has been calculated to over 1 trillion digits past the decimal betoken.
The distance around a circumvolve is chosen thecircumference. The distance across a circle through the eye is chosen thebore. is the ratio of the circumference of a circle to the bore. Thus, for any circle, if you split the circumference past the diameter, yous get a value shut to. This relationship is expressed in the following formula:
where
is circumference and
is diameter. You lot can test this formula at home with a round dinner plate. If you measure the circumference and the diameter of the plate and then split by, your caliber should come close to. Another mode to write this formula is:
where· means multiply. This second formula for finding the circumference is commonly used in problems where the diameter is given and the circumference is non known (see the examples below).
Theradius of a circumvolve is the distance from the centre of a circumvolve to any betoken on the circle. If you place two radii end-to-finish in a circumvolve, yous would take the same length equally one diameter. Thus, the diameter of a circumvolve is twice as long equally the radius. This relationship is expressed in the following circumference of a circle formula:
, where is the bore and
is the radius.
Circumference, diameter and radii are measured in linear units, such as inches and centimeters. A circle has many different radii and many different diameters, each passing through the middle. A real-life example of a radius is the spoke of a bicycle bike. A 9-inch pizza is an example of a bore: when one makes the starting time cutting to piece a round pizza pie in half, this cut is the diameter of the pizza. So a 9-inch pizza has a nine-inch bore. Let'southward expect at some examples of finding the circumference. In these examples, we volition use = three.14 to simplify our calculations.
Example 1: The radius of a circle is 2 inches. What is the bore?
Solution:
= 2· (2 in)
= 4 in
Example 2: The diameter of a circle is iii centimeters. What is the circumference?
Solution:
= *
= iii.14· (iii cm)
= ix.42 cm
Case iii: The radius of a circle is 2 inches. What is the circumference?
Solution:
= two· (two in)
= 4 in
= *
= three.14· (4 in)
= 12.56 in
Example 4: The circumference of a circle is 15.vii centimeters. What is the bore?
Solution:
= *
15.7 cm = 3.14·
fifteen.7 cm÷ 3.xiv =
= fifteen.7 cm÷ 3.14
= five cm
Summary: The number is the ratio of the circumference of a circle to its diameter. The value of is approximately 3.14159265358979323846...The diameter of a circumvolve is twice the radius. Given the diameter or radius of a circle, we can detect the circumference. We can besides detect the diameter (and radius) of a circle given the circumference. The formulas for diameter and circumference are listed below. Nosotros circular to 3.14 in order to simplify our calculations.
= *
For additional help, picket the Circumference of a Circle video
Exercises
Circumference of a circle questions: Click once in an ANSWER BOX and blazon in your answer; then click ENTER. Afterwards you click ENTER, a bulletin will appear in the RESULTS BOX to indicate whether your answer is correct or incorrect. To get-go over, click CLEAR. Use = iii.14 to calculate your answers.
| 1. | The bore of a nickel is 2 centimeters. What is the circumference? |
| two. | The circumference of a bike bicycle is 50.24 inches. What is the diameter? |
| 3. | The radius of a round rug is four anxiety. What is the circumference? |
| four. | The circumference of a compact disc is 28.26 centimeters. What is the radius? |
| 5. | The diameter of your cycle bicycle is 25 inches. How far will you move in i plow of your wheel? |
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Source: https://www.mathgoodies.com/lessons/vol2/circumference
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