Converting Units of Measurements

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Objective

The students will be able to determine which operation is needed for a conversion.

Big Idea

Again and again and again.

Opener

15 minutes

Today’s lesson involves setting up how to determine which operation will need to be used in order to convert units.  The idea is that students understand that when going from a smaller unit of measurement to a bigger unit they will need to divide.  Conversely, students will also understand that going from a bigger unit of measurement to a smaller unit they will need to multiply.

I begin the lesson by reviewing the Graphic Organizer that we created yesterday and the history associated with the two systems.  I ask students to describe the information that we added yesterday.  By doing this quick review I can check for understanding of yesterday’s concepts. 

Okay, so what are we studying in this math unit?  (Measurement)  And so based on our graphic organizer we broke the concept of measurement into two main parts.  What are the two main parts of measurement?  (U.S. Customary System and Metric System)  Within these two systems we are going to investigate four different parts of each.  What parts of each system of measurement are we going to be studying?  (Length, weight, capacity, and temperature).

In the previous lesson students measured the length of the hallway using cubits.  My goal was that students discovered the challenges associated with using a non-standard unit of measurement.  It was difficult for them to use the cubit because their arm is attached to them and each person has a different size forearm.

While you were working with your Egyptian groups yesterday what would have made measuring our pyramid easier?  Tell your neighbor. 

Practice

30 minutes

I now lead students on a discovery of how to convert amongst units.  It is important that students are able to determine which operation to use for converting.  I want them to be able to create an easy example in which they can refer back to again and again to check that they are using the correct operation.  I guide them in their thinking to create this simple tool as a reference for converting. 

Today we are going to focus on determining the operation needed for converting.  If we are talking about length, what are some units that you might use measure?  (inches, feet, yards, miles)  Okay what do you know about inches and feet?  (There are 12 inches in one foot.) 

I write this on the board and then begin to dig further into this simple equation.  Here is a video of my thought process on creating an example for students to use when converting.

Once students journey through this example we create a small tool to recap this knowledge.  I give students a few examples and ask them what operation they would use to solve the problem.  At this time I am not focusing on the numbers associated with the operation but strictly the specific operation needed. 

What would we need to do if we were converting from feet to inches?  What about from inches to miles?  Come up with a question you can ask your neighbor to check for their understanding of determining the operation needed.  Check it out.

I then have students show me with a thumbs up if their partner got the question correct or thumbs down if their partner got it wrong.  I have students share some questions they asked their neighbors and their responses.  I also ask students to explain their thinking when reporting the responses. Students should be able to justify their response by discussing the relative sizes of the units.  For example, if the student says they should divide to go from inches to miles, the student should be able to rationalize that inches are smaller than miles so you would need to divide to find the answer.  

Closer

15 minutes

Again today’s lesson is intended to set up an example that the students can use over and over to determine the operation needed to convert amongst units within a system of measurement.  I want students to be very comfortable with the 12 inches = 1 foot formula.

As an exit slip I have students explain in writing how they will use this formula to determine which operation to use for converting.