The area of the trapezoid can be calculated by:
A = 1/2 (b1 + b2) (h)
In the diagram, the two parallel sides of the trapezoid (bases) are 50 yards and 30 yards, and the height is 40 yards.
Plugging these values into the formula:
A = 1/2 (50 + 30) (40)
A = 1/2 (80) (40)
A = 40 (40)
A = 1600 square yards
Therefore, 1600 square yards of rubber will be needed for the park.