How Far is a Light-Year?
A light-year is a unit of length used by astronomers to measure
interstellar distance (the distance between stars). A light-year is
defined as the distance that light will travel in a year. If the speed of
light is 186,000 miles per second (300,000 km per second), then calculate the distance that light will
travel in one year. Express your answer in miles per year.
[Note: Cancel similar units above and below the dividing line. This
process is known as "dimensional analysis."]
186,000 mi/sec x 60 sec/min x 60 min/hr x 24 hr/day x 365 days/yr