Here the Greek letter p represents a constant approximately equal to 314159 which is equal to the ratio of the circumference of any circle to its diameter. The next equations show how you can instead find the diameter from them. To calculate the diameter of a circle multiply the radius by 2.
Learn how to find the area and perimeter of a parallelogram.
Its just twice as long. What is its circumference perimeter. If you dont have the radius divide the circumference of the circle by p to get the diameter. The next equations show how you can instead find the diameter from them.