Help finding the circumferance of a circle

It sounds like you are trying to determine the surface area of a cylinder.

The area of the top and the bottom of the cylinder (which are circles) are pi x r ^ 2. Since there are two of them, we have to multiply this answer by 2.

The surface area of the side is going to be the circumference of the circle times the height. The circumference is 2 x pi x r and the height is 15 inches.

To get the total surface area, we have to add these amounts together.

Good luck,

Paul

area formula is PI x r squared
that is 3.1417 times the radius of the circle squared
example is:- 3.1417 times 3 inches squared =3.1417 times 3x3=3.1417x9=28.279 square inches if you want to work back from a circumference measurement, the formula for circumference is 2 x PI x radius or PI x diameter
if you have a circumference of 12 inches then the dia is calculated 12 inches = dia x PI to get the diameter , divide the 12 inches by PI and that will be the diameter so that is 12 divided by 3.1417 =3.819 inches
now you can go from the first formula the radius is the diameter divided by 2 so the radius will be 3.819 divided by 2 = 1.909 inches
so applying the area formula it becomes 3.1417 times 1.909 times 1.909 =11.458 square inches
to find your answer simply substitute the dimensions in place of the example figures.in the relevant formula.

Answer is A. Divide area by pi to find the circumference. (153.86/3.14 = 49) Determine the square root of the circumference to find the radius. (sqrt of 49 = 7)

If you would like to know the circumference of a 15" diameter circle this is the formula:
circumference = radius x 2 x pi
circumference = diameter x pi

in our case:
circumference = 15" x 3,14
circumference = 47 ,1" (that's 119,634 cm)

a. radius is 7 inches and circumference is 43.96 inches.

Pi is a mathematical constant whose value is the ratio of any Euclidean plane circle's circumference to its diameter; this is the same value as the ratio of a circle's area to the square of its radius. It is approximately equal to 3.14159265 in the usual decimal notation.

You find the area of the larger circle. Then find the area of the smaller circle. Then to get the area of the ring, you subtract the area of the smaller circle from the larger circle.

So basically:

Area of larger circle - Area of smaller circle = Area of ring
http://www.vitutor.com/geometry/plane/concentric_circles.html
pi. r2 = area 2pi. r=circumference of circle.

Read more: http://wiki.answers.com/Q/What_is_the_Formula_for_concentric_circle#ixzz1Cv8wAOJf

what class are you in? Is this your home work? Anyway, You should know that
Circumference = 2 x pie x radius therefore radius - circumference / 2 x pie in this case radius = 30 x 7 / 2 x 22 = 210 / 44 Now you can calculate that fraction.

Hello my friend, I am Jonas I work as a programmer in some various programming languages. Here try this code:
This program is design to output the Diameter, circumference, and area given a radius of a circle. #include <iostream.h> int main() { int radius, diameter, circumference, area, pi; cout << " Enter the radius of a circle\n"; cin >> radius; pi = 3.14159; diameter = 2 * radius; circumference = 2 * pi * radius; area = pi * (radius)^2; cout << "Diameter formula executing.....(2 x r)\n"; cout << "Diameter is " << diameter << endl; cout << "circumference formula executing.....(2 x pi x r)\n"; cout << "circumference is " << circumference << endl; cout << "area formula executing......(pi x [r x r])\n"; cout << "area is " << area << endl; return 0; }
Also if you need tutorial you can visit this site Learning C++ .Hope this solution will able to help your problem solved. If you need more assistance just reply to this post or send me a mail at [email protected] you and Godbless.

You cannot have a semicircle that has a diameter of 2.500 mm and a radius of .425mm and a circumference of 3000mm

Circumference is equal to pi times the diameter. pi is = 3.14

The radius of a circle is always 1/2 the diameter

Area of a circle is pi time the radius squared


Loringh