To answer this question you would need to know the formula for the area of a circle, . You would start by squaring 400, getting 160,000. You would then multiply 160,000 by 3.14, getting 502,400 meters squared as your answer.
Well I'm not sure what the answer would be since I'm not that smart but I did get the answer of 90, I did this by dividing 72 by 80 which equals .9 and I multiplied that by 100 and got 90.