Converting Customary Measures Lesson Topic Index | Grade 5 Math | Intermediate Test Prep | StudyZone

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!

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

2. 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? 12 or 3 or 36 or 5280 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