Hey there!
The equation for the area of a circle is A=pi r^2. Plug in 4.7 for r. You get A=3.14 x 4.7^2. Simplify to get A= 3.14 x 22.09. Multiply to get 69.36. Since only half the circle is shaded, divide 69.36 by 2. You get 34.7. The answer would be 34.7 yd^2.
I hope this helps!