We can calculate the area of a circle using the following formula:A = pi x r2The area we are given is 16pi. Therefore, we can divide both sides by pi. So,16pi = pi x r2becomes16 = r2We can squareroot both sides to calculate the value of r. sqrt16 = sqrt r2Therefore r = 4We can then use the formula d = 2r to calculate the diameter. Therefore the diameter of the circle is 2x4 = 8cm.