Sometimes it is necessary to convert units from one measurement system to another or convert within a system (for example, from kilometers to meters). For Example, conversion factors between SI and U.S. customary units of length are as follows: `1 mi l e = 1,609 m = 1.609 km` `1 m = 39.37 i n. = 3.281 ft` `1 ft = 0.304 8 m = 30.48 cm` `1 i n. = 0.0254 m = 2.54 cm (exactly)`

Example 1:

Convert `15.0 i n.` to `cm` `15.0 i n.= (15.0 i n.)((2.54 cm)/(1 i n.)) = 38.1 cm`

Example 2:

A car is traveling at a speed of `38.0 m//s`. Is the driver exceeding the speed limit of `75.0 mi//h`? Convert `m//s` to `mi//h`: `(38.0 m)/(1s)((1 mi)/(1609 m))((60s)/(1mi n))((60mi n)/(1h))=85.0 mi//h`