Since the area of a circle is A = pi x r^2, and you know A, you can divide 153,86 by pi. What gives you 48,97515909. That means r^2 = 48,975... you can calculate r by taking the square root of your answer, that gives you 6,998225424. And since the diameter is two times the radius, the diameter would be 13,99645085. I think.
