# Converting Measurements Using Ratios Day 2

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## Objective

SWBAT: • Use ratios to convert measurement units using multiplication or division. • Convert measurements between the customary and metric system. • Apply knowledge of measurement conversions to solve word problems.

#### Big Idea

Which building is the world’s tallest building? Students use ratios to convert measurements between customary and metric systems. Students apply this knowledge to word problems.

## Do Now

3 minutes

See my Do Now in my Strategy folder that explains my beginning of class routines.

Often, I create do nows that have problems that connect to the task that students will be working on that day.  Today I want students to quickly review the measurement facts that they are expected to know on our state test.   We check the answers together.  I stress to students that they need focus on memorizing these facts.

## Conversion Review

5 minutes

I tell students to get out their foldables from the previous lesson.  They can use it as a resource to complete the conversions.  As students work, I walk around to monitor student progress.  I am looking to see that students are using the correct measurement fact as well as setting up and labeling their ratios.  Students are engaging in MP5: Use appropriate tools strategically.

We come back together and I ask students to share out their strategies and answers to problem 4.  I want students to realize that 7,000 pounds is equal to 3 ½ tons.

## Comparing Measurements

5 minutes

I have a volunteer read the information and the question.  Students participate in a Think Pair Share.  Students are engaging in MP2: Reason abstractly and quantitatively and MP3: Construct viable arguments and critique the reasoning of others.   I call on students to share their thinking.   I ask students how that fact can help us determine whether Kate or Alexa is taller.  I want students to realize that if 1 inch is equivalent to 2.54 centimeters, we can use that fact to convert other amounts.  We set up the ratios together and determine which girl is taller.

## Practice

10 minutes

Students work in partners on the problems.  I walk around and monitor student progress.  My goal is that the students complete problem 1.  If they complete problem 1 successfully, they will move on to problem 2.  A common mistake is to incorrectly set up or label the ratios.  I do not teach students to multiply when changing a “smaller” unit to a “larger” unit, or vice versa.  I believe that this short cut does not help students; rather it is one more procedure that they are likely to mix up or forget.  By using ratios, I believe students are able to understand that converting measurements is just creating equivalent ratios.

If students are struggling, I may ask one or more of the following questions:

• What units are involved in the problem?
• What are you trying to find?
• How can you use the information to create ratios?
• What operation are you going to use to create equivalent ratios?

With a few minutes left, I call on students to share their thinking to problem 1.  I call on students to share if they agree or disagree and why.  Students are engaging in MP3: Construct viable arguments and critique the reasoning of others.

## Dr. Evil and Mini-Me

20 minutes

We watch the first video clip.  http://robertkaplinsky.com/work/mini-me/#prettyPhoto  I ask students, “What is the ratio, in inches, of Mini-Me’s height to Dr. Evil’s height?”  I explain to students that they will be working with their partner on this task.  There is information on this page and the next page that will help you.   I remind students that they can look back at their practice problems to get ideas.

As students work, I walk around and monitor student progress and behavior.  Students are engaging in MP1: Make sense of problems and persevere in solving them and MP2: Reason abstractly and quantitatively.

If students struggle, I may ask one of the following questions:

• What are you trying to figure out?
• What do you know?
• What extra information do you need?
• How does this problem relate to the practice problems we did?  How is it different?

If students successfully answer the question, I may ask one of the following questions:

• How did you find your ratio?
• What does your ratio actually mean?
• Challenge Questions

We come back together for the last 5 minutes.  Students share out their ratios and how they got them.  Then we watch the second video clip.  I ask students, “Why is your ratio different?  Which ratio is more reasonable?”  Students are engaging in MP2: Reason abstractly and quantitatively.   I want students to realize that if the ratio of Mini-Me to Dr. Evil was really 1/8, then for every 1 inch of Mini-Me’s height, Dr. Evil would have 8 inches of height.  Just by looking, we can see that Dr. Evil isn’t 8 times taller than Mini-Me.

## Closure and Ticket to Go

7 minutes

I ask students why they would need to convert units from one system to another.  I pass out the Ticket to Go and the HW Converting Measurements Using Ratios Day 2.