Working With Units
I. Steps
a. Take what you are starting with and put it over 1.
b. Set up a “Factor Label” problem so that the units that you start with will cancel.
(optional)
Draw a small map using arrows of the units that you need to go
through to get to the end result.
c. Look up conversion factors.
d. Complete the factor label problem so that all units cancel except the ones that you are ending
with.
e. Check work
i. Make sure that all fractions are equal to each other top to bottom
ii. Make sure that all intermediate units divide out
II. Math and Units
a. Adding/Subtracting- resulting units are the same
i. 2 in + 2 in = 4 in
b. Multiplication- resulting units are squared or hyphenated
i. 2 in X 2 in = 4 in2
ii. 2 in x 2 cm = 4 in-cm (rare occurrence and not “proper”)
c. Division- units cancel each other out or resulting units are separated by a / read as per
i. 2 in ÷ 2 in = 1
or
ii. 2 in ÷ 4 cm = 2 in/cm
Examples of working with units:
Example of a really hard one: Convert 5miles per hour to m/s.
(optional step)mi.  km m
and
hr. min  sec.
5 mi
1.6 km
X
1hr.
1000 m
X
1 mi.
1 hr.
X
1km
1min.
X
60 min.
8000 meters
=
60 sec.
=
3600 seconds
2.22 m/s