What is a unit conversion and can you give me an example?

Units are labels like "miles", "feet", "hours", "seconds", etc.

If you want to change 60 miles/hour into feet/second,

you'll have to change miles into feet and hours into seconds.

There are 5280 feet in one mile and 3600 seconds in one hour (60 seconds in each minute and 60 minutes in each hour, so you have 60 x 60 = 3600 seconds in one hour):

To change miles into feet, multiply the number of miles by the fraction:  5280 feet / 1 mile  (you can do this since 5280 feet and 1 mile represent the same distance, so you are really multiplying by 1/1 or 1).

To change hours into seconds, multiply the number of hours by the fraction:  3600 seconds / 1 hour; since hours is on the bottom of 60 miles/hour, multiply by the fraction 1 hour/3600 seconds.

So:  60 miles/hour · (5280 feet/1 mile) · (1 hour/3600 seconds)

     =  [60 · 5280 · 1 feet] / [1 ·3600  seconds]  =  88 feet/second

(The miles in the numerator cancelled the miles in the denominator; the hour in the denominator cancelled the hour in the numerator.)

(You can change the labels "miles" to "mile" and "seconds" to "second" when ever you want to.)

2 dm = 8 inches