To find:
The area of the rectangular cardboard.
Solution:
The length of the cardboard is 34 inches and the width is 20 inches. The diameter of the semicircle is 20 inches and the radius is 10 inches.
The area of the rectangular cardboard is the difference between the area of the rectangle and the semcircle.
Thus, the area of the cardboard is 522.86 inch^2.