## 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."]
Solution:

186,000 mi/sec x 60 sec/min x 60 min/hr x 24 hr/day x 365 days/yr