Q&A for How to Calculate the Area of a Circle

If the object is a circle, and you know its circumference, you would divide the circumference by pi to find the diameter of the circle. Half the diameter is the radius. Square the radius and multiply by pi to find the area of the circle.

To find the circumference of a circle, simply multiply the diameter by pi (3.14). For example: If d= 23cm, C= 3.14 x 23cm, so C= 72.22cm.

C = pi * d calculates the circumference (distance around the outside of the circle). D in the formula refers to the diameter which is the width of the circle. The formula for the area of a circle is A = pi * r * r where r is the radius (diameter / 2).

Divide the area in square centimeters by 10,000 to find the area in square meters.

Half the diameter is the radius. Square the radius and multiply by pi to find the area.

Knowing for sure requires seeing a cross section. You wouldn't be asking, I presume, if you could see the inside. If the pipe was made after WWII, try a comparison. Measure the outside circumference of the pipe, or the outside diameter using something like calipers. Note the material; PVC, copper, iron and then go to a hardware store that sells pipe. Find a pipe of the same material and exterior dimensions, and measure its interior.

Square the fraction, and multiply by pi.

Most basically, you will need to find the areas of each circle separately, and then add them up. Somewhere in your problem, you must be provided with the radius of each circle, or some way of determining the radius, diameter or circumference of each circle.

You will need to know some more data about the size of a chick and the size of the round box. It is possible that your problem includes the radius of a chick and the radius of the round box. Calculate the areas, and divide the total area of the box by the area taken up by one chick.

You convert inches to feet the same way to find the area of a circle as you do to find anything else. 1 foot = 12 inches, or 1 inch = 1/12 foot. (If you're asking how to convert from square inches to square feet, divide the number of square inches by 144 to get square feet.)

Use the diameter to find the area of the circle, and then multiply that by the height to find the volume. If d=60 ft, then r=30 ft. Then A=pi*r^2, so the area = 900pi sq.ft. The volume of the tank is equal to the area times the depth, so V =900pi*1 = 900x3.14x1 = 2826 cubic feet

Do the aforementioned steps, just in reverse. Divide by pi, then find the square root. You will then have the radius.

Area is A = pi * r^2, where r is the circle's radius. Since a semicircle is half of a circle, we can simply divide that equation by two to calculate the area of semicircle. So, the formula is A = (pi * r^2)/2.

The ratio of the areas is the square of the ratio of the radii. For example, if the ratio of the radii is 2:3, the ratio of the areas is 4:9.

πr²: (3.14)(0.3)² = (3.14)(0.09) = 0.2826 square millimeter.

Double the radius, and multiply by pi.

Divide the area by pi. Find the square root of that number.

Go here for an explanation: MathOpenRef.com/CircleAreaDerive.html.

I suspect that what you really need to find is the area of a ring, which the center circle hollow. To do this, you need to find the area of the outside circle, using A=pi*r^2. Then find the area of the inner circle, and just subtract. You need to be told the radius of at least one of the circles. You cannot find the solution if all you know is the distance between the two circles.

pi times (6 squared). Just use the formula above and you'll be fine.

44 equals pi multiplied by the diameter. 44 = πd. Then d = 44 / π = 44 / 3.14 = 14. The radius is half the diameter. So r = 7. The area is πr² = π(7)² = 49π = 153.86 square centimeters.

A = πr² = (3.14)(25)² = (3.14)(625) = 1,962.5 sq cm.25π^2.

The formula for the radius of a circle is r = √(A/π). So divide 36 by pi, then find the square root of the quotient.

Divide the area by pi. Then find the square root of that quotient. Double the square root. That's the diameter.

Use the usual formula, A = πr². The radius is 5½ inches.

If you mean the circle's radius is 1/2 mile, the area is πr² = (3.14)(½)² = 0.785 square mile.

Multiply 22/7 by the square of the radius.

If D is the diameter, take half of it, which is the radius, square the radius and multiply by pi.

In your example you would have to know the length and width of the rectangle and the radius or diameter of the semicircle. Multiply the length of the rectangle by its width to get its full area. Then find the area of the semicircle, which would be half of pi multiplied by the square of the radius. Then subtract the area of the semicircle from the full area of the rectangle.

πr² = 44. r² = 44 / π = 44 / 3.14 = 14. r = √14 = 3.74 cm.