Find the Equivalent Customary Unit

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SWBAT to convert between customary units of measure.

Big Idea

Multiplication and division help you convert from one unit to another.

Whole Class Discussion

15 minutes

To start this lesson, the students are sitting at their desks with a sheet of paper.  I tell them that in today's lesson, we are taking what we know about various units of measurement, and we are going to convert units.  That means we are going to change them from one unit to another unit.  We have already learned about units of length.  We learned that we can measure length with inches and feet.  Which is smaller, inch or foot?  Student response:  inch.  It is very important to know this because we will need to know that to convert units.  I continue questioning the students to review what they have learned.  I find that questioning is a good strategy to check for understanding.  With units of weight, ounces and pounds, which one is smaller? Student response:  ounces.  Unit of capacity - cup and pint, which is smaller?  Student response:  cup.  We will need to know all of this to convert units.  In order to convert units, we use two operations.  Before we decide the operation, we need to know which one is larger or smaller.

I have the students turn in their math books to a customary unit of weight chart.  This chart shows how the different units are equivalent.  On the Smart board, I display the Teaching Tool-Units of Measure to help guide the students understanding of converting units.   

 I instruct the students to write 8 tons = ___ pounds on their paper.  I let the students know that we are trying to convert from tons to pounds.  I'm trying to see how many pounds we will have in 8 tons.  I tell the students to look at the chart in the book and tell me what it says about tons and pounds.  Student response:  1 ton = 2,000 pounds.  On the white board, I write 1 ton = 2,000 pounds.  I let the students know that when they are trying to convert from one unit to the next, they must go to the chart and see what it says.  We use that information to help us convert.  

I have the students write on their paper, "To change larger units to smaller units, you multiply."  I ask, Which unit is larger, tons or pounds? Student response:  Tons.  I let them know that because we are changing from a larger unit to a smaller unit, we should multiply.  The chart tells us that every 1 ton is 2,000 pounds.  I have 8 tons.  What am I going to multiply to see how many pounds we have?  Student response:  8 x 2,000.  This gives us 16,000 pounds.  

I explain to the students why we multiply when changing from larger units to smaller units.  I give them the example of pouring a gallon of milk into cups.  I let the students know that when I pour that 1 gallon of milk into cups, it will take more than 1 cup.  The number of cups will be greater than 1.  That is why we multiply to change larger units into smaller units.  

I share with the students another strategy to use to find this answer.  I have the students draw a chart on their paper.  

In the chart, we write the rule 1 T = 2,000 lb.



















To give the students practice with changing from a smaller unit to a larger unit, we work 6 cups = ____ pints.  I have the students go to the chart to find what it says.  The chart tells us that 1 pint = 2 cups.  I point out to the students that we are changing cups to pints.  I ask, Are cups smaller or larger than pints?  Student response:  smaller.  On their papers, I have the students write, "To change from a smaller unit to a larger unit, you divide."  To solve this problem, we use the information from the chart.  As the students write on their papers, I write 6 divided by 2 = 3.  Again, I like for the students to have more than one strategy to solve a problem.  I instruct the students to draw another table to convert from cups to pints.









Last, we discuss how to compare units with greater than, less than, and equal to.  I write on the board, as the students write on their paper, 5 pt ___ 4 c.  I let the students know that when they compare different units, they must convert one unit to the other unit.  In other words, they can't compare pints and cups.  

I told the students to decide which unit they want to change.  For example, are they going to change pints to cups or cups to pints.  For the purposes of being consistent in the whole class discussion, I asked the students to change pints to cups.  The students referred to the chart to find that 1 pt = 2 cups.  How many pints do we have?  Student response:  5.  Are we changing from larger to smaller or smaller to larger?  Student response:  larger to smaller.  Therefore, we must multiply.  5 x 2 = 10 cups.  Which sign goes in the blank?  Student response:  greater than.   


Skill Building/Exploration

20 minutes

For this activity, I let the students work as pairs to match the correct equivalent customary units.  By doing this, it allows the students to hear their classmates thinking on the skill (MP3).  

I give each pair a Converting Customary Units sheet and bag with the Matching Pieces for Unit Conversion.  The students must determine which customary units are equivalent by using strategies such as multiplying, dividing or drawing a chart.  The students are required to work together on each item.  As the pairs discuss the problem, they must be precise in their communication within their groups using the appropriate math terminology for this skill (MP6). As you hear in the Video - Converting Units of Measure, the students must use reasoning to find their answers.

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

1. What does the custumary unit of measure chart tell us?  

2.  What strategies can you use to find the equivalent number?

3.  Are you converting from a smaller unit to a larger unit or a larger unit to a smaller unit?

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.

My Findings:

I found that the students knew how the units compared in reference to being larger or smaller.  However, with there being different pieces in the bag, it proved difficult for quite a few pairs to focus in on one number to find the equivalent measure.  Therefore, I had to stop the lesson and share the solution that one pair had already found.  We discussed the fact that a large number, 10,560 feet, was in the bag.  I told the students that because it is such a large number, we can look in the conversion chart to see what unit of measure can go with this large number.  This had to be 2 miles becasue 1 mile is 5,280 feet.  This proved to help out quite a bit.  The students started focusing in on one number and looking for its equivalent.


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 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 - Customary Units and Student Work), 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.