Lesson 2

The purpose of this warm-up is to elicit the idea that a centimeter is the length of the edge of a centimeter cube and to connect this with the length of a base-ten block composed of 10 centimeter cubes. This will be useful when students measure with base-ten blocks and report their measurements in centimeters in a later activity. While students may notice and wonder many things about these images, discussion of the attributes of the shapes are emphasized by the labels and the meaning of a centimeter are the important discussion points. Students use and revise their language to clearly describe the images (MP6).

• 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.

• “How are the labels on both images the same? How are they different?” (They both show the length of one square. They both show 1 length unit. One says centimeter and one says cm.)
• “Both labels show the length of 1 centimeter. Centimeter is a long word and can be hard to use to label your length units. We can use cm for short. ‘C’ represents centi and ‘m’ represents meter.”
• Display a centimeter cube and 10-centimeter tool.
• “If the length of 1 edge of a centimeter cube is 1 centimeter, how long is this block? Explain.” (It’s 10 centimeters long because it shows 10 blocks put together. Each block is 1 centimeter long.)
• “When we practiced adding and subtracting by place, we used these tools to show ones and tens.”
• “When we measure we will call them centimeter cubes and 10-centimeter tools to describe their lengths.”

The purpose of this activity is for students to transition from expressing the length of objects as a count of physical length units (for example, 12 cubes) to expressing the length of objects using a standard unit (for example, 12 centimeters). Students use centimeter cubes and 10-centimeter tools (base-ten blocks) to measure the length of an earthworm. Throughout the activity, students make connections to place value and describe the convenience of different types of tools based on their length (MP5).

• Groups of 2
• Give centimeter cubes and 10-centimeter tools to each group.
• Give each student a copy of the bearded dragon.
• “Yesterday we measured the length of Priya’s iguana. An iguana is a reptile. What do you know about reptiles?”
• Share responses.
• Display the image.
• “This is a drawing of a bearded dragon. Like iguanas, bearded dragons are a kind of reptile that are often kept as pets.”

• “Measure the length of the bearded dragon using the centimeter cubes. Then use the 10-centimeter tool to measure the length.”
• 10 minutes: partner work time
• Monitor for students who answer the last question by using:
  • only centimeter cubes
  • only 10-centimeter tools
  • a combination of 10-cm tools and centimeter cubes.

• Share and display student measurements for the last problem.
• As needed, select previously identified students to demonstrate their responses to the following discussion questions.
• “How can you prove that the bearded dragon is 24 centimeters long with only centimeter cubes?” (Start at one end and line up the cubes until you reach the other end. You can count the cubes because each cube is 1 centimeter long.)
• “How can you prove the bearded dragon is 24 cm long with 10-centimeter tools?” (Start at one end with one 10-centimeter tool, then keep lining up more 10-centimeter tools until you go past the end. You can count the first two by 10, then start counting by ones until you get to the block that lines up with the end.)
• “Which tool was easier to use to measure the length of the bearded dragon?” (I liked using the 10-centimeter tools because you could measure faster without having to use as many blocks. It was easier to count.)

The purpose of this activity is for students to practice measuring and expressing the length of objects in centimeters. Students measure the length of different reptiles and choose whether to use centimeter cubes, 10-centimeter tools, or a combination of the two tools (MP5).

• Groups of 2
• Give each student a Reptile Length sheet and access to base-ten blocks.

• “Use the tools that make sense to you to find the length of each reptile. Then compare your measurements with your partner. If any measurements are different, measure the reptile again together to find a length you agree on.”
• “Then decide how much longer the day gecko is than the threadsnake together. Show your thinking using drawings, numbers, or words.”
• 5 minutes: independent work time
• 5 minutes: partner work time
• Monitor for students who use:
  • centimeter cubes to measure lengths shorter than 10 cm
  • 10-centimeter tools to measure lengths shorter than 10 cm
  • a combination of centimeter cubes and 10-centimeter tools
  • only the 10-centimeter tools to measure lengths that are longer than 10 cm

If students use centimeter cubes to measure longer reptile lengths, consider asking:

• “How did you decide which tools to use to measure the ____?”
• “How could you use the 10-centimeter tool to measure the next reptile?”
• “How could you use both tools to measure?”

• Invite previously identified students to share how they measured a length that was shorter than 10 cm (A or E).
• Invite previously identified students to share how they measured a length longer than 10 cm (B, C, D, or F).