|To get the exact answer, you can use the formula for the area of a circle. The formula is:
Pi (¼, a Greek letter) is the ratio of a circle's circumference (the distance around a circle) to its diameter. This always works out to be the same answer no matter the size of the circle. In fact, Pi is a decimal number that no one has discovered completely -- we know it to more than a hundred decimal places. Its okay to use the short approximation of 3.14 instead of 3.1415927... I can't remember the rest of it, but you get the point!
The r stands for the radius of the circle.