Explore Customary Units of Length

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SWBAT understand the relative sizes of units within one system of measurement.

Big Idea

The students will record the appropriate measurement units in a two-column table.

Whole Class Discussion

15 minutes

Today's lesson focuses on customary units of length.  My students know relative sizes of units within one system of measurement.  The students will learn to convert between and record the appropriate measurement units in a two-column table (4.MD.A1). 

On the Smart board, I have the following website to teach the lesson:


I let the students know that length means how long something is.  I also share that "customary" units are what is used in the United States.  I refer to the webiste were there is a fork and a ruler.  I point out to the students that the fork is being measured in inches (which is a customary unit of measurement).  

There are some common units of length that are used in the US.  Common means "done often or used often."  These are things that you should be accustomed to hearing from third grade.  The customary units of length are:  inches, feet, yards, and miles.  Let's get an idea of how long these customary units of length are by using a ruler and other items.  I give each student a ruler.  I tell the students to find an inch on their fingers.  I share that sometimes they may need to measure something, and they may not have a ruler available.  I let them know that if they know where an inch is on their finger, they can use their finger to estimate the measurement of an item. I show the students how to find 1-inch on their finger.  

The smallest customary unit of length is the inch.  As you just learned, you can find 1-inch on your finger and it gives you an idea of the size of an inch.  Next, is a foot (ft).  I ask the students to hold the ruler up.  I remind the students that a ruler is 12 inches long and that 1 foot = 12 inches.  Therefore, 1 foot is the length of the ruler.  If I was measuring something longer than a 12-inch ruler, then I can measure it in feet.  If I wanted to measure something smaller than this ruler, then I must use inches.  

The next unit of measure is the yard(yd).  I hold up the ruler and remind the students that we said that one ruler is 12 inches.  I point out on the board that this site tells us that 1 yard = 36 inches.  How many rulers does it take to make 1 yard?  Student response: 3.  What is bigger, yards or feet? Student response:  yards.  I tell the students that there is one last measurement to discuss before I let them explore.  The last measurement is miles.  I let the students know that we will not be able to find anything in the classroom to compare to miles because it is way longer than anything in this classroom.  On the board, it tells us that 1 mile = 1,760 yards.  To give them an idea of this, I explain to the students that this would be the length of three rulers put together 1,760 times.  Another way to compare miles is 1 mile = 5,280 feet.  That is 5,280 of the rulers laid out next to each other, back to back.  This gives the students a mental picture of how large miles are compared to yards, feet, and inches.  



Skill Building/Exploration

20 minutes

For this activity, I let the students work as pairs to explore and determine the correct customary unit of length to use to measure certain items.  By doing this, it allows the students to hear their classmates thinking on the skill.  

I give each pair a Customary Units of Length Activity Sheet, a plastic bag with items, and a ruler.  The students must determine the correct customary unit of length to use to measure items found in the classroom. The students are required to work together on each item.  They should be in the same location in the classroom together.  I do not allow one student to work one problem, while the other student is finding the answer for the next problem.  That is not collaboration, and they must collaborate.  In the Video - Unit of Length, you hear the students discuss the lesson.

 As they work, I monitor and assess their progression of understanding through questioning. 

1. Is the item larger than the unit of length that you are using?  

2.  What is the most reasonable unit of length to use?  

3.  Can you use a different unit of length?  How do you know?

4.  If you use inches when you should have used yards to measure an item, how would it effect the time taken to measure the item?

As I walk around the classroom, I am questioning the students and looking for common misconceptions among the students.  Any misconceptions are addressed at this point, as well as whole class at the end of the activity.



15 minutes

To close the lesson, I bring the students back together as a whole class.  I feel that it is very important to let the students share their answers as a whole class.  This gives those students who still do not understand another opportunity to learn it.  I like to use my document camera to show the students' work during this time.  Some students do not understand what is being said, but understand clearly when the work is put up for them to see.

I feel that by closing each of my lessons by having students share their work is very important to the success of the lesson.  Students need to see good work samples (Student Work - Unit of Length), as well as work that may have incorrect information.  More than one student may have had the same misconception. During the closing of the lesson, all misconceptions that were spotted during the group activity will be addressed whole class.  In this particular lesson, I reiterate to the whole class that the answer does not include the word "square" because we are adding to find the total number of feet or inches that make up the perimeter of a shape.