Here we will answer the following three questions. a) What is 18Pi? (What is 18π?), b) What is the area of a circle if the radius is 18?, and c) What is the circumference of circle if the radius is 18?
18π is another way of writing 18 times Pi (18 x 3.14). Therefore, the answer to our first question is:
18π = 56.55
Area: Next, we will calculate the area of a circle if the radius is 18. The formula for the area of a circle is πr2, which means that the area of a circle with a radius of 18 is:
π182 = 1017.88
Circumference: Finally, we will calculate the circumference of a circle if the radius is 18. The formula for the circumference of a circle is 2πr, which means that the circumference of a circle with a radius of 18 is:
2π18 = 113.10
Note: π or Pi has an infinite number of decimals. For our calculations on this page with a radius of 18, we used Pi with eleven decimals as 3.14159265358 and then we rounded all our answers to two decimals.
Helpful Definitions:
Radius: The distance between the center of a circle to the edge of the circle. In our example on this page it was 18.
Diameter: The distance between one side of a circle to the exact opposite side of the circle. This is the same as 2 times radius. (For example, if the radius is 18, then the diameter must be 36.)
Pi: The ratio of a circle's circumference to its diameter. This is a fixed number regardless of circle size.
We used the following formulas on this page, where A is Area of circle, C is Circumference of circle, and r is radius:
A = πr2
C = 2πr
Pi Calculator
Go here to look up another number using our popular Pi Calculator.