Question

the speed of light in a vaccum is about 3.00 x10^8m/s to determine how many km a pulse from a lazer beam travels in exactly one hour

Answer 1

Distance = (speed) x (time)

Distance = (3 x 10⁸ meter/second) x (1 hour)

Distance = 3 x 10⁸  meter-hour per second

Distance = 3 x 10⁵ kilometer-hour per second

Hmmm.  That answer is perfectly correct and totally useless.  We have no idea how far one meter-hour per second is.  It's a unit we never use.  We'd better convert the answer to a unit of length that we use every day.

(3 x 10⁵ km-hour/sec) x (3,600 sec/hour) =

(3 x 10⁵ x 3,600)  (km-hour-sec/hour-sec) =

1.08 x 10⁹ km

THAT's it !  A pulse of light in vacuum travels 1.08 billion km in one hour.