how to find the circumference when radius is given?

Question

pls mention the formulae & show an example?

Answer 1

circumference = 2 x pi x radius
if radius = 5, then circumference = 10 pi, or about 31.415928

Answer 2

A circle is a shape with all points the same distance from the center. It is named by the center. The circle to the left is called circle A since the center is at point A. If you measure the distance around a circle and divide it by the distance across the circle through the center, you will always come close to a particular value, depending upon the accuracy of your measurement. This value is approximately 3.14159265358979323846... We use the Greek letter (pronounced Pi) to represent this value. The number goes on forever. However, using computers, mathematicians have been able to calculate the value of to thousands of places.

The distance around a circle is called the circumference. The distance across a circle through the center is called the diameter. is the ratio of the circumference of a circle to the diameter. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to . This relationship is expressed in the following formula:

where is circumference and is diameter. You can test this formula at home with a round dinner plate. If you measure the circumference and the diameter of the plate and then divide by , your quotient should come close to . Another way to write this formula is: where · means multiply. This second formula is commonly used in problems where the diameter is given and the circumference is not known (see the examples below).

The radius of a circle is the distance from the center of a circle to any point on the circle. If you place two radii end-to-end in a circle, you would have the same length as one diameter. Thus, the diameter of a circle is twice as long as the radius. This relationship is expressed in the following formula: , where is the diameter 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 center. A real-life example of a radius is the spoke of a bicycle wheel. A 9-inch pizza is an example of a diameter: when one makes the first cut to slice a round pizza pie in half, this cut is the diameter of the pizza. So a 9-inch pizza has a 9-inch diameter. Let's look at some examples of finding the circumference of a circle. In these examples, we will use = 3.14 to simplify our calculations.


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Example 1: The radius of a circle is 2 inches. What is the diameter?
Solution:
= 2 · (2 in)
= 4 in

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Example 2: The diameter of a circle is 3 centimeters. What is the circumference?
Solution:
= 3.14 · (3 cm)
= 9.42 cm

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Example 3: The radius of a circle is 2 inches. What is the circumference?
Solution:
= 2 · (2 in)
= 4 in

= 3.14 · (4 in)
= 12.56 in

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Example 4: The circumference of a circle is 15.7 centimeters. What is the diameter?
Solution:
15.7 cm = 3.14 ·
15.7 cm ÷ 3.14 =
= 15.7 cm ÷ 3.14
= 5 cm

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Summary: The number is the ratio of the circumference of a circle to the diameter. The value of is approximately 3.14159265358979323846...The diameter of a circle is twice the radius. Given the diameter or radius of a circle, we can find the circumference. We can also find the diameter (and radius) of a circle given the circumference. The formulas for diameter and circumference of a circle are listed below. We round to 3.14 in order to simplify our calculations.

Answer 3

Hi! This is Anup. Your question is quite easy to answer. Here it goes-

The basic formula for finding out circumference of a circle is as follows:-
c = 2 x π x r.
where,
c = circumference of circle which is to be found out,
π = constant & π = 3.14
r = radius of circle.

For example, consider r = 2, i.e radius of circle is 2,

Then we can find out it's circumference using the above discussed formula as follows :-

c = 2 x π x r

c = 2 x 3.14 x 2

c = 12.56 sq.units. is the required answer.

Hope my answer has satisfied your question.

Goodbye & Best luck !!!

Answer 4

What a silly question ... Dont you have a book or internet for this??? Why do you waste this space ....???

But I answered this for two points !!!!!

Perimeter or Circumference = 2 x Pi x Radius (or Diamater x Pi)
Area = Pi x Square of Radius

Now dont ask what is Pi !!! Pi is a mathematical constant which is an irratioanl real number with a value of 3.1415 or 22/7.

Answer 5

Circumference of a circle is given by 2*pi*radius. If you are not using calculator or computer, you can use 355/113 as approximate value of pi.

Answer 6

Radius = r = 2 ins

Pie = 22 x 1/7 = 3.142 ( mathematical constant).

Radius Square = rxr = 2x2 = 4

circumference = 2 x pie x Radius. = pie x Diameter circumference = 2 x 3.142 x 2
circumference = 12.568 ins

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Area= 22/7xradius square.
= 22/7x4
= 3.142 x 4
= 12.568 square ins or ins square.

Use your calculator with pie key, it will give you slightly different answer and more decimal places.

PS

I have taken 2 ins for the purpose to show that circumference and area can be numerically same in this special case.

Please note that the units of area and units of circumference are not the same.

Answer 7

The formula is
2* pie *r
two times 22/7 *radius
or diameter *22/7
diameter *3.14

if you do not know how to apply the formula . do ot bother about the circumfrence of the circle .Under the circumstances , the teacher will himself / herself give you a perfect circle . you do not distort the circumfrence .

Answer 8

Hey!!

Hoping that this is no kinda joke.....

If "r" is the radius then the circumference will be 2 .(pi).r

pi = 22/7

good luck!!

Answer 9

circumference = 2(pi)r where pi=3.14 or22/7 and r is the radius

Answer 10

simple C= 2pi *r where r is radius.

pi is approximately 22/7
so if r = 7 cm then c approximately 2*22/7 *7 or 44