How to calculate the area of a circle?

Answer 1

A = Pi * r^2

Answer 2

How to Calculate the Area of a Circle
A circle is one of the most interesting geometric shapes but is one of the more difficult ones to understand. Follow these steps to find the area of a circle. You will also learn how to find the area of a sector, which is a slice of a circle, similar to the shape of a slice of pie or pizza.


Steps [edit]Note the formula. The formula for finding the area of a circle is: area = pi x radius squared.


Use the formula to calculate the area of the circle. This formula allows you to calculate as follows:
Take pi (3.14159265) and multiply it by the radius and multiply the radius again (pi x radius x radius).
Note the difference between radius and diameter. Radius is the distance from the center of the circle to the edge of the circle. This is not to be confused with diameter which is the distance from the edge of the circle, through the center and to the edge of the circle (i.e. twice the radius).


Find the area of a sector. This time you are working with a slice of the circle, like a piece of pizza or cake and finding its area is a little more complex. The formula is the arc angle divided by 360-degrees, multiplied by the area of the circle. Finding that arc angle is the complex part.


Use a protractor for a small circle. If you’re doing this using a circle or sector on a piece of paper, simply use a protractor to find the angle. Place the straight edge on one side of the sector and find where the other edge lines up.
Use the objects around for larger circles. If you’re doing this using something on a larger scale, such as flooring, try a different approach. Think of your slice as part of one huge circle, and the curved wall (if flooring is the example) is just a portion of the edge of that circle. The radius is a wall or line from one end of the curved wall to the opposite side that isn’t curved.
Find the circumference of the circle. The formula for the circumference is pi x diameter. Diameter is twice the radius and pi is 3.14159265:
Multiply these and you have found the total length of the edge of the circle.
Take this number and divide by 360. This will give you the length of each degree of the circle.
Place tick marks or make notes on a piece of paper using the length of each degree as increments. For example, if the radius of the big circle is 12 feet (3.657 meters), then the total length of the edge of the circle is 75.36 feet (22.969 meters) (pi x diameter). The length of each degree, therefore, is 0.209 feet (or approx 2.5 inches) (6.35 cm) .
However many increments (example = 2.5 inch increments) it takes to measure out the length of the curved wall is the number of degrees the angle is. Using the example, if it takes 25 increments, or 62.5 inches (1.587 meters), then the arc angle is approx. 25 degrees.
Now apply this number to the formula. Using the example, divide 25 degrees by 360. Then multiply by the area of the circle (pi x 12 feet (3.657 meters) squared = pi x 144). The total area, therefore, is 31.38 square feet (9.564 meters).

Answer 3

The area of a circle is the square of the radius multiplied by pi, an irrational number nearly equal to 22/7.

A = (pi) * r^2

In exam or assignment questions, it is generally better not to approximate pi unless the value of pi to be approximated is given with the question. They'll always give only pi = 22/7 or pi = 3.14. If the value of pi is not mentioned, never approximate. They will cut marks. This is from personal experience.

Answer 4

the area of a circle is given by the formula

area = Pi x r^2 (Pi times radius squared)

where r is the radius of the circle. for greater accuracy using a calculator is highly recommended instead of using 3.14 as Pi.

Answer 5

area of a circle = pi x r^2

Answer 6

the area of a circle formula is :

A= Pi X r ^2 (Pi X R squared)

If given a value for the diameter of a cirle, divide the diameter by two. this will be your radius

Answer 7

Pi x r squared. Say you have a circle 6 inches in diamater, the radius is 3 inchs. The radius squared is 3 x 3= 9.
9 x 3.14= 28.26.

Answer 8

the formula to find the area of a circle is pi x r^2.

pi is 3.14 and r stands for the radius of the circle. First you square the raidus and then you multiply it by 3.14.

Answer 9

Area = Pi * Radius * Radius.

Answer 10

The formula would be

A= r^2(pi)

Area= (square) the radius x 3.14159