Warm-up: Choral Count: Beyond 100 (10 minutes)
The purpose of this Choral Count is to invite students to practice counting by 1 beyond 120 and notice patterns in the count. These understandings help students develop fluency and will be helpful later in this lesson when students will need to use centimeters and meters to record lengths. For example, some students may record 1 meter and 30 centimeters as 130 centimeters.
Students may wonder about the place value of three-digit numbers. Although students are not expected to understand the hundreds place yet, be prepared to say that the 1 means 1 hundred without going too far. Unitizing 100 will be addressed in a later unit.
- “Count by 1, starting at 20.”
- Record as students count.
- Stop counting and recording at 30.
- “Count by 1, starting at 120.”
- Record as students count directly below the first count.
- Stop counting and recording at 130.
- “What patterns do you see?”
- 1–2 minutes: quiet think time
- Record responses.
- “Who can restate the pattern in different words?”
- “Does anyone want to add an observation on why that pattern is happening here?”
- “Do you agree or disagree? Why?”
Activity 1: Reptiles to Measure (20 minutes)
- Tape strips of these lengths on the floor. Label each strip with the letter and the name of the reptile. (It may be helpful to make multiple sets of the strips to keep the groups small.)
- Tape A, gila monster: 58 cm
- Tape B, baby alligator: 72 cm
- Tape C, baby cobra: 44 cm
- Tape D, komodo dragon: 180 cm
- Tape E, adult alligator: 3 meters and 36 cm
- Tape F, adult cobra: 1 meter and 90 cm
- Tape G, ribbon snake: 2 meters and 82 cm
- Groups of 3–4
- Give students access to centimeter rulers and base-ten blocks.
- Display the reptile images.
- “In previous lessons, we measured different kinds of smaller reptiles. What do you know about some of these larger reptiles?”
- “Let’s imagine we are zookeepers who need to measure the lengths of these reptiles.”
- “Some of these reptiles would be too dangerous to bring in the classroom to measure. I’ve placed strips of tape on the floor to represent their lengths.”
- “Look at the strips of tape on the floor. Choose anything we’ve used so far to measure each of the strips A through D with your group. You can use centimeter cubes, 10-centimeter tools, the rulers you made, or the centimeter rulers.”
- “Record the length of these four reptiles in centimeters.”
- 10 minutes: small-group work time
- Monitor for different ways students use their tools to measure the komodo dragon:
- iterating 10-centimeter tools
- iterating rulers
- iterating a combination of tools
Each length of tape on the floor represents the length of a reptile.
A: gila monster
B: baby alligator
C: baby cobra
D: komodo dragon
Measure to find the length of each reptile. Don’t forget the unit.
- What is the length of a gila monster?
- What is the length of a baby alligator?
- What is the length of a baby cobra?
- What is the length of a komodo dragon?
Advancing Student Thinking
- “Can you show me how you measured the __?”
- “How could you use your rulers to find the same measurement?”
- “Which measuring tool did you choose to use? Why?” (We used the 10-centimeter tools and cubes because they were easier to count tens and ones. We used the rulers because we didn’t have to use as many blocks. It was faster.)
- Invite previously identified students to share how they measured the komodo dragon and calculated its length.
- “What was challenging about measuring longer lengths in centimeters?” (We had to line up our tools and count the centimeters. Centimeters are small so there were a lot of them to count.)
- “Would you want to use these tools to measure real large reptiles?” (No. It’d take too long. I might get bit.)
- “What would make measuring longer lengths easier?” (We could use a tool that has more centimeters on it. We could use a longer length unit to measure.)
Activity 2: Measure with a Meter Stick (15 minutes)
The purpose of this activity is for students to learn about the meter as a longer metric unit of length. Students measure longer lengths with a new tool, the meter stick. Students measure strips of tape of different lengths and choose between a centimeter ruler and a meter stick in order to measure each. In the synthesis, students share their measurements of each line and discuss how they chose which tool to use to measure (MP5). Students measure Strips D–G in this activity. Students measure the komodo dragon (Strip D) twice to experience measuring the same length with a ruler and a meter stick. They discuss and compare their measurements in the lesson synthesis.
- Groups of 3–4
- Give each group a meter stick.
- “We saw that measuring longer lengths with centimeters can be challenging. Luckily, there is a standard unit that is much larger than a centimeter that we can use. It’s called a meter.”
- Show students a meter stick.
- “This is called a meter stick. The length of one end to the other is 1 meter long. Just like we used centimeter cubes at first to measure centimeters. We can use the length of a meter stick to measure length in meters.”
- “What do you notice about the meter stick?” (There are lots of little lines; the numbers go up to 100; every tenth number is bold)
- 30 seconds: quiet think time
- Share responses.
- “The meter stick makes it easier to measure longer lengths. We can use the meter stick to measure in meters or centimeters.”
- “Find 50 cm on the meter stick.”
- If time permits, find a few other markings.
- “Now, let’s go back to our job as zookeepers and measure some even larger reptiles.”
- “You are going to measure the komodo dragon again and 3 new reptiles."
- “You may use any of the measuring tools you have used today. Be prepared to explain why you chose each tool.”
- 12 minutes: group work time
- Monitor for the different ways students measure the ribbon snake and adult alligator including how they record their measurements in meters.
D: komodo dragon
E: adult alligator
F: adult cobra
G: ribbon snake
- Measure the length of the komodo dragon in meters.
- What is the same or different about your measurements for the komodo dragon from Activity 1 and Activity 2?
Measure each reptile in centimeters or meters. Don’t forget the units.
- How long is an adult alligator?
- How long is an adult cobra?
- How long is a ribbon snake?
Advancing Student Thinking
If students do not measure using the meter stick, or only report their measurements in centimeters, consider asking:
- “About how many meters long is the __?”
- “What is different about measuring the __ in meters (or meters and centimeters) rather than only centimeters?”
- “Which tools did you use to measure Strip G, the ribbon snake? Why did you choose this tool?” (We used the meter stick and took away 10 because it was so close.)
- “What did you do when you found that Strip E, the adult alligator, was longer than 3 meters but shorter than 4 meters?” (We saw it was closer to 3 meters so we said it was about 3 meters. We used the meter stick 3 times and then the cm ruler for the rest.)
“Today, we learned about another standard unit of length—the meter. We used meter sticks to make measuring longer lengths a lot easier.”
“You measured the length of the komodo dragon two times. What was the same or different about your measurements?” (When we measured in meters it was only about 2 meters. When we measured in centimeters it was 180 centimeters. We only had to use the meter stick 2 times to measure the whole length. We had to use the ruler lots of times.)
Display the meter stick.
“What did you like about using the meter stick? When do you think it is helpful to use a meter stick to measure instead of a ruler or other tools?” (I liked using it for the longer lengths because you didn’t need as many tools or you didn’t need to move the tool a bunch of times. It’d be good to use to measure longer things. If you were measuring meters you would want to use it.)