Well a yard is 3 ft so divide 3 into 13 3 goes into 13 4 times and you get 12 you have 4 whole yards and 1 ft left or 1/3 of a yard. :) hoped this helped
Since the formula for the area of a circle is Pi x r squared, the area would be 81 x Pi (you teacher may want you to use Pi as 3.14 or put it in your calculator).