
Scientific Notation
One lightyear is the distance light travels in a 365day year. The speed of light is about 186,282.4 miles per second.
(a) How long is one light year (in miles)? Express your answer in scientific notation.
(b) Light from the North Star takes 680 years to reach the earth. How many miles is the North Star from the earth?

(a) One 365day year = 31,536,000 seconds. Multiply this by 186,282.4 mi/sec and you'll have the distance of one light year in miles. Convert that to scientific notation.
(b) Multiply the answer in (a) by 680. (Note that I am disregarding leap years here.)