Lesson 7

This warm-up prompts students to consider the same object being measured with different length units to set students up to measure with different units in the next activity.

• Groups of 2
• Display the image.
• “What do you notice? What do you wonder?”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Share and record responses.

• “Can anyone restate _____’s idea?”

The purpose of this activity is for students to measure the same length using three different length units. Students choose which units they would like to use. When groups compare their measurements, they notice that although they measured the same length, they got different measurements. They consider why this could be and determine that when they use a different size length unit, they get a different number to describe the length. Some students may notice that the number of units needed depends on the size of each individual length unit, but this is not a discussion point until grade 2.

• Create sets of 30 connecting cubes, 50 base-ten cubes (centimeter cubes), twenty 2-inch paper clips, and twenty 1-inch paper clips for each group.
• Put 18-inch strips of tape on the floor for each group. 

• Groups of 2–4
• Give each group access to the different length units.
• “Who wears the biggest shoes in your family?”
• Share responses.
• “How long do you think your shoes will be when you are grown up?”
• Share responses.
• “A man named Jeison Orlando Rodriguez Hernandez holds the record for having the longest feet in the world. He has to have his shoes specially made because stores don't sell shoes big enough.”

• “There are strips of tape on the floor that show the length of Jeison’s foot. You will measure the length of his foot using different objects.”
• Read the task statement.
• 12 minutes: partner work time
• “Compare your measurements with another group. What do you notice?”
• 2 minutes: small group discussion

• “What did you notice when you measured the length of Jeison's foot using different objects?”
• If needed, ask, “Why did we get different numbers when we used different objects?” (The objects we used had different lengths. Some were shorter and some were longer. We used more small cubes to measure the length than any other object.)

The purpose of this activity is for students to use what they have learned about measuring length to determine whether measurements are accurate. Students understand that they need to use same-size units to be precise in their measurements (MP6).

• Groups of 2

• Read the task statement.
• 8–10 minutes: partner work time
• Monitor for students who can explain whose measurements are accurate and whose are not accurate and why.

If students say that Clare's measurement is inaccurate because she did not use connecting cubes or because the measurement is not 15, encourage students to tell you more about what they mean. Consider asking:

• “How is the way Clare measured like how we measured objects in the last activity?”
• “Did Clare measure the entire length of the shoe with the small blocks?”
• “How are the small blocks the same? How are they different?”

• Display the image for Jada’s measurement.
• “Is Jada’s measurement accurate? Why or why not?” (It is not accurate because there are gaps between some of the cubes.)
• Display the image for Kiran’s measurement.
• “Is Kiran’s measurement accurate? Why or why not?” (Kiran’s measurement is not accurate because the cubes are different sizes.)
• “What could Kiran change to make his measurement accurate?” (He could use all connecting cubes or all the little cubes, instead of using some of each.)
• “When we measure a length with objects it is important that each object has the same length.”