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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.
Example 1: The radius of a circle is 2 inches. What is the diameter? Solution: = 2 · (2 in) = 4 in
Example 2: The diameter of a circle is 3 centimeters. What is the circumference? Solution: = 3.14 · (3 cm) = 9.42 cm
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
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
Courtesy of Ms. Goodies Math Page
A circle does not have a volume. It is a 2-dimensional thing, which has an area. and a perimeter which has a length (circumference). A cylinder, like a tube with closed ends has a volume equal to the area of the base (usually a circle, dicussed above) multiplied by the length of the cylinder.
What else can I help you with?
How many miles in a 21 mile radius?
If the area is a circle and the radius of the circle is 21 miles, the distance around the circle (circumference) is 131.95 miles. The area of that circle is 1,385.4 square miles.
How many square feet is a circle with a radius of 3000 feet?
Area of a circle = pi*radius squared Not that 30 inches = 2.5 feet
What is the equation for surface area?
with a tape measure To calculate the area of a rectangle, you multiply the length times the width. To calculate the area of a square, you multiply one side times another side. To calculate the area of a circle, you multiply the diameter times pi (that's 3.1416). To calculate the area of a triangle, you multiply the height times the base, and divide by 2.
What is a circumscribed polygon?
A circumscribed polygon is a polygon all of whose vertices are on the circumference of a circle. The circle is called the circumscribing circle and the radius of the circle is the circumradius of the polygon.
What keeps things moving in a circle?
gravity keeps us in a circle
What is formular of circle?
Area of a circle: pi times radius squared Circumference of a circle: 2 times pi times radius or diameter times pi
What do you call the perimeter of a circle?
The perimeter of a circle is called the circumference and the formular of finding it is Pi D or 2Pi R
How can the base area of a cube be found?
by using formular
What is the formular for a circle?
In Cartesian coordinates:(x - a)2 + (y - b)2 = R2(a, b) is the center-point of the circleR is the circle's radius.
The formular for circumference of a circle is?
c=πdorc=2πrBasically, the circumference is either π times the diameter of the circle or π times twice the radius.π (Pi) can be approximated as 3.14159
What is the circumference of the circle if the diameter is 24 meter?
half of a diametre is radius. hence multiply the diameter by 0.5 then use the formular of cicumference, which is 2*pie*r
How do you find the area of a circle if the circle is 8cm?
Area of a circle = pi*radius2
How do you get an area for a circle?
Area of a circle = Pi * radius2
How you get the area of circle?
Area of a circle = pi*radius2
What is An area of circle?
The area of a circle is the amount of space inside the circle. The area of a circle is calculated by multiplying pi(3.14159) by the radius squared.
Help with math how do you get the area of a circle?
Area of a circle is calculated by A=2*p*r where A represents the circle's area and r is the radius of the circle.
If the area of one circle is twice that of another circle what is the ratio in percent of smaller to larger circle?
If the area of one circle is twice that of another, the ratio of the area of the smaller circle to the larger circle is 1:2. To express this as a percentage, the area of the smaller circle is 50% of the area of the larger circle. Thus, the ratio in percent of the smaller circle to the larger circle is 50%.
