Diameter = circumference/pi
Diameter = circle's circumference/pi
You multiply the circle's diameter by 3.14 (Pi) to get the circumference.
The circumference of a circle with a diameter of 18 inches is 56.5 inches.
Divide the circumference by Pi.
multiply the diameter times pi (3.14159265)
Multiply the diameter by the constant pi.
Diameter of a circle = circumference/pi
pi times diameter
Divide the known circumference by pi to find the diameter of the circle.
circumference of a circle = pi*diameter or 2*pi*radius
Since circumference is found by multiplying pi by the diameter of the circle, the diameter can by found using the inverse operation. diameter = circumference/pi