To find the volume of the silo find the volum of the hemisphere with radius of 15 feet and add the volume of the cylinder with a radius of 15 feet and a height of (100 - 15) = 85 feet.
The total volume = 1/2 * 4/3 π (15)^3 + π (15)^2 * 85
find the volume of a sphere with a radius of 15 ft and divide by 2 (because there is only half a sphere on top of the silo).
then add the volume of a cylinder with a radius of 15 ft and a height of 85 ft (because we need to deduct the radius of the sphere from the total height to get the height of the cylinder itself).