What is a common source for a voltage difference

Light from the sun reaches the earth in 8.3 minutes. the velocity is 3.00 x 10^8 m/s. how far is earth from the sun? i know how to get to d = (3 x 10^8 m/s)(498 sec). i just don't know how to get from there to the answer being 1.5 x 10^11 m.

Anybody wanna ? (picture included? )

If the force applied to an object remains constant, is more power needed for the object to move faster ? explain