The loading dock's height forms one leg of a right triangle. The ramp and the ground for the hypotenuse and other leg respectively. We are told that the ramp is at a 30 degree angle. Usually that is angle to the ground. This would make the 30 degree angle, opposite the 5 ft height of the loading dock. The Sin 30=1/2, and in this triangle would equal 5/h where h is the length of the hypotenuse which is the length of the ramp. If we cross multiply 5/h=1/2 we find h=10. The ramp would be 10 ft long.