Start with the** identity property of multiplication.**

anything multiplied by 1 is equal to itself.

**The rule of divisibilty**

*any number divided by itself is equal to 1*

Let’s convert 20 meters to feet. We need a conversion factor:

by the rule of divisiblity:

note that I put the units I want to end with (feet) on top.

we know that

and since we can do this:

the meters cancel out:

and all we are left with is the multiplication:

or:

#### Discussion

As long as you have a conversion factor between the two things you are converting you can do this. You are always multiplying by 1 and canceling out the units of measure. It gets kind of mechanical.