Unit Analysis
Unit analysis means using the rules of multiplying and reducing fractions to solve problems involving different units.
Example 1:
A desk is 
feet long. Find the length of the desk in inches.
There are 12 inches in 1 foot. Write this relationship as a fraction, and multiply it by the given length.
Note that you can cancel the unit "ft" just as though it were a number being multiplied.
Example 2:
A car can drive 80 miles on $6 worth of gasoline. If 1 gallon of gasoline costs $2.50, find how far the car can travel in kilometers on 1 liter of gasoline.
To solve this problem you need to know some conversions.
1 kilometer (km) 
0.62 miles (mi)
1 gallon (gal) 3.79 liters (L)
Write all the conversions as fractions, so that the unwanted units will cancel.
