A hemisphere is half a sphere.
So, the volume of a hemisphere is the half of the volume of the complete sphere.
The formula for the volume of a sphere is:
V = (4/3) π (radius)^3
Using π = 3.14 and radius = diameter / 2 = 50 feet / 2 = 25 feet.
You get:
V = (4/3) (3.14) (25 feet)^3 = 65,416.7 feet^3
Answer: 65,416.7 cu. ft.