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How To Find The Area Of A Circle With Diameter/Radius – Formula, Examples

Area of Circle

Area of a circle is the number of square units inside that circle. The fixed point is called the center of the circle. And fixed point and point path together make radius of the circle. Point path is called the perimeter of the circle.

Students who are in search of How To Find The Area Of A Circle With Diameter/Radius, Formula to Calculate Surface Area, Perimeter and Circumference, must check formula with example here.

Area of Circle

Radius of the circle: The radius of the distance between the perimeter of the circle is called the radius of the circle.

Diameter of the circle: If the radius of the circle is doubled, it is called the diameter of the circle.

Chord of the radius circle: The chord of the circle never passes through the center of the circle. The largest diameter of the circle is the diameter of the circle.

Formula to Calculate

Area Of A Circle Is

π (Pi) times the Radius squared: A = π r2
or, when you know the Diameter: A = (π/4) × D2
or, when you know the Circumference: A = C2 / 4π

Surface Area of Circle

Sphere = 4 pi r 2
Cylinder = 2 pi r 2 + 2 pi r h

Perimeter of Circle

C = pd or C = p2r 

Circumference of a circle


Check Also: Maths Formulas

How To Find The Area Of ​​The Circle?

Area Of Circle formula 1 Circle Area

Calculate the length of radius: If you only know the diameter (distance from one side of the diameter or circle to another) (or it is measured), then divide it by 2 to get the radius. Radius of a normal circle / circle is always half of the diameter.

Formula fall: The formula for finding the area of ​​a circle / circle is the area = πr 2 (r squared)

For scavenging the radius, multiply it by itself: For example, if your radius was 6 centimeters, then the radius-screwed 36 centimeter skewer would be done.

Multiply the result obtained from step 3 by (π) the result:

Use it in “Find the area of ​​a field”.

If the instructions say “leave it in the period of pie” or “do it completely”, then put the pie only with your answer (for example, the area of ​​the circle = π36 centimeter²).

If you only round it up to 3.14, then this is not exactly right. There is no other way to show it correctly without leaving the pie mark.

If the instruction says anything about rounding, replace the pie instead of 3.14 or use the pivot button of your calculator.

You May Read This: How to Prepare for Maths

How to Remember?

Area of Circle

Area Of Circle formula 2 Area of ​​a field Area

Find out how big the field is in terms of degrees: Unfortunately, there is no definite way to do this. Depending on the information given in the problem, these pathways will be quite different and it is not possible to include a step-by-step process for each such path.

Find out the radius of the cycle: Again, the radius will be exactly the diameter of the diameter.

Find out the area of ​​the circle: For instructions on this topic, see the section above.

Make a fraction:

Your matrix should be:

The central angle of the field (in degrees) as the numerator, and

360 degrees; As the denominator Simplify the fraction for the shortest period: Find out the least common denominator to simplify your fraction.

Multiply that fraction with the area of ​​the circle: 

Your work is over!

Alternatively (instead of simplifying the fraction), multiply the area of ​​the circle with the degree of area and then divide by 360 degrees

Example: What is the area of a circle with radius of 3 m ?

Radius = r = 3

Area= π r2

 = π × 32

 = 3.14159… × (3 × 3)

 = 28.27 m2 (to 2 decimal places)

Check Out: Logarithms Formulas

Comparing a Circle to a Square

A circle has about 80% of the area of a similar-width square.
The actual value is (π/4) = 0.785398… = 78.5398…%

Why? Because the Square’s Area is w2
and the Circle’s Area is (π/4) × w2

Example: Compare a square to a circle of width 3 m

Square’s Area = w2 = 3= 9 m2
Estimate of Circle’s Area = 80% of Square’s Area = 80% of 9 = 7.2 m2
Circle’s True Area = (π/4) × D2 = (π/4) × 3= 7.07 m2 (to 2 decimals)
The estimate of 7.2 m2 is not far off 7.07 m2

A “Real World” Example

Example: Max is building a house. The first step is to drill holes and fill them with concrete.

The holes are 0.4 m wide and 1 m deep, how much concrete should Max order for each hole?
The holes are circular (in cross section) because they are drilled out using an auger.
The diameter is 0.4m, so the Area is:

A = (π/4) × D2
A = (3.14159…/4) × 0.42
A = 0.7854… × 0.16
A = 0.126 m2 (to 3 decimals)
And the holes are 1 m deep, so:

Volume = 0.126 m2 × 1 m = 0.126 m3

So Max should order 0.126 cubic meters of concrete to fill each hole.

START NOW: Mathematics Quiz

Instruction For the Students!!!

  • Try to remember the formula during the exam.
  • Do not forget that you have to skew radius, not diameter.
  • Note that 3.14 is only an approximation of pie. In fact, there are infinitely many digits after the decimal point, so use a calculator.
  • To remember the formula, write it in a notebook or letter.
  • If you cannot find any further help, ask a friend or a member of the family, search the internet or look in a math book.
  • It is convenient to keep a calculator with you. A simple 4-function will be right, but more complex calculators can store your measurements, which you will be able to use later. Or maybe you can use them on your computer.

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