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# What is the area of a circle with diameter 9.99 miles?

Here is the answer to questions like: how to find the area of a circle with diameter 9.99 miles?

Use the this circle area calculator below to find the area of a circle given its diameter, or other parameters. To calculate the area, you just need to enter a positive numeric value in one of the 3 fields of the calculator. You can also see at the bottom of the calculator, the step-by-step solution.

### Inputs:

 Radius: or Diameter: or Circumference: Unit: centimeter foot inch kilometer meter mile yard

### Result:

The area of a circle with diameter 9.99 is 78.38

### Area of a cicle in terms of radius:

Area = π . r2 = 3.14 Ã— 52 = 78.38 square miles.

### In terms of diameter:

Area = π . (d/2)2 = 3.14 Ã— (9.99/2)2 = 3.14 Ã— (5)2 = 78.38 square miles.

### In terms of circumference:

Area = C2/(4π) = 31.382/ = 984.7/(4 Ã— 3.14) = 984.7/(12.56) = 78.38 square miles.

Note: for simplicity, some results may be rounded to nearest hundredth and π was rounded to 3.14. See formula details below in this page.

### A circle of radius = 4.995 or diameter = 9.99 or circunference = 31.38 miles has an area of 78.38 square miles which is equal to:

• 203 square kilometers (kmÂ²)
• 203000000 square meters (mÂ²)
• 2030000000000 square centimeters (cmÂ²)
• 50160 acres (ac)
• 20300 hectares (ha)
• 242800000 square yards (ydÂ²)
• 2185000000 square feet (ftÂ²)
• 314700000000 square inches (inÂ²)
• ## Formula for area of a circle

Here a three ways to find the area of a circle (formulas):

### Circle area formula in terms of circumference

See below some definitions related to the formulas:

### Circumference

Circumference is the linear distance around the circle edge.

The radius of a circle is any of the line segments from its center to its perimeter. The radius is half the diameter or r = d/2.

### Diameter

The diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. The diameter is twice the radius or d = 2r.

### The Greek letter π

π represents the number Pi which is defined as the ratio of the circumference of a circle to its diameter or π = C / d. For simplicity, you can use Pi = 3.14 or Pi = 3.1415. Pi is an irrational number. The first 100 digits of Pi are: 3.1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 ...

### Note:

If you input the radius in centimeters, you will get the answer in square centimeters (cmÂ²), if in inches, will get the answer in square inches (inÂ²) and so on ...

Circumference is often misspeled as circunference.

You can use our area unit converter to see the results in other units.

### Disclaimer

While every effort is made to ensure the accuracy of the information provided on this website, we offer no warranties in relation to these informations.