In this lesson you will learn how to convert, or change,
one unit to another.
It
is really easy once you know the two simple questions you must ask
yourself!

Am I
going from smaller unit to larger, or larger to smaller?
(thus divide or multiply)

What
conversion factor will I use?
(more on that later)
First, a quick review of the customary equivalent units of length.
Length 
12 inches (in) = 1 foot (ft) 
36 inches = 3 feet = 1 yard (yd) 
5280 feet = 1 mile (mi) 
The "conversion factors"
are the numbers that when used change one unit to another. In the
customary system the conversion factors are 12, 3, 36, or
5,280.
Conversions 
Here
are those two questions again, and those questions are the same
for both metric and customary conversions (but use different
numbers for conversion factors!).
 Do I multiply or divide?

To change from a
larger unit of length to a smaller unit of length,
multiply.

To change from a
smaller unit of length to a larger unit of length, divide.
2. What is my
conversion factor?

Let's start with a
simple conversion: 
How many inches are
in 5 feet? 
5 feet = ___ inches 
Think: 1 ft = 12 in and
changing from larger unit (feet) to smaller unit (inches) so
must multiply. 
So MULTIPLY
5 by 12
5 x 12 = 60 
5 feet = 60 inches 
Now let's try another
conversion, still simple, but using a different operation!
How many yards are in
15 feet?

15 feet = ___ yards

Think: 3 ft = 1 yd and changing from a smaller unit
(feet) to a larger unit (yards), so must divide.

So
DIVIDE 15 by 3
15 ÷
3 = 5 
15 feet = 5 yards 
OK, now on to some more difficult
conversions! But remember you still either divide or multiply , and the
conversion factors are the same (3, 12, 36, or
5,280)
14 in =
_______ft ______ in

Think: 12 in = 1 ft and changing from smaller unit (in)
to larger unit (ft) so must divide. 
So DIVIDE
14 by 12
14 ÷ 12 = 1 and 2 left over 
That 2 "left over" is 2 inches
so
14 in = 1 ft 2 in

2½ miles = ____ feet

Think: 1 mile = 5280 ft and changing from larger unit
(mi) to smaller unit (ft) so must multiply. 
So MULTIPLY
5280 by 2½
5280 x 2½ = 10,560 + 2640 = 13,200 
2½ miles = 13,200
feet

Remember these two
questions when converting units: 

Am I changing from smaller
to larger unit (divide), or from larger to smaller ( multiply)? 
What is my conversion
factor? 12, 3, 36, or 5280 
Ready to Practice?
