Area of a circle is 
. The first one, a, the radius squared is 8*8=64. So 
. If you multiply in pi as 3.14, you'll have 200.96 square inches. The second one, b, the radius squared is 10*10=100. So 
square kilometers. If you multiply in pi as 3.14 you'll have 314 square kilometers. The third one, c, the radius squared is 14*14=196. So 
. Or you could multiply in pi as 3.14 to get 615.44 yd squared. For the last one, d, the radius squared is 22*22=484 cm. Therefore, 
, or multiply in 3.14 for pi to get 1519.76 cm squared. There you go!