Is 27 the radius or diameter? If it is the diameter, divide 27 in half and then do the following steps with your new number. I will do it assuming 27 is the radius/1. Do the number to the second power. The second power means you do the mean times itself two times. So 27*27. That is 279,2. Next times that by pi, or 3,14. So 279*3,14 is 876,06. That's your answer. I hope I helped!