Lesson 1

The purpose of this warm-up is to invite students to share what they know about measuring. Students measured the length of objects in grade 1 using non-standard units such as paper clips and tiles and may also have experience measuring length outside of school. This warm-up allows teachers to hear the language students use to talk about measurement and what attributes of objects they attend to in order to measure.

• “What do you know about measuring?”
• 1 minute: quiet think time

• Record responses.

• “What does it mean to measure?” (To find out how long something is.)
• “We are going to continue thinking about what we know and learn more about measuring in our upcoming activities.”

The purpose of this activity is to emphasize the importance of identifying the length of a unit when measuring (MP6). Students work in groups to measure the same length of string using straws. Students find and report measurements of different lengths because they are provided with straws of different lengths. In the synthesis, students discuss that although the same length of string was measured, the measurements are different, because different length units were used. This sets students up to discuss what happens when everyone uses the same length unit in the next activity.

Straws may be replaced by pipe-cleaners or other rigid objects that can be cut to the specified lengths.

This activity uses MLR8 Discussion Supports. Advances: Listening, Representing

• Create a 40-cm length of string or ribbon for each group of 2–3.
• Create five 10-cm length straws for half of the groups of 2–3.
• Create ten 5-cm length straws for half of the groups of 2–3.

• Groups of 2–3
• Give each group a set of straws (some groups get 10-cm long straws and others get 5-cm long straws) and a string that measures 40 cm long.
• Display the image.
• “What do you know about this animal? What could you measure?”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.

• “Priya has a pet iguana. She thinks he may be ready for a new cage and wants to know how long he is.”
• “First, Priya used a piece of string to measure the length of her pet. She started at the iguana’s head and stretched it all the way to its tail. She cut the string so it was the same length as her iguana.”

MLR8 Discussion Supports

• Use gestures to emphasize how Priya might measure the length of the iguana. For example, when describing how Priya uses the string, use your hands to emphasize one end of the string at the head, pull the string taut, and emphasize the end at the tail.
• “Each group has a piece of string that is the same length as Priya’s string.”
• “You are going to measure Priya’s string using the straws at your tables.”
• 5 minutes: small-group work time
• As students work, monitor for students from each group (short straws and long straws) who line up the straws end to end with no gaps or overlaps to share their method in the synthesis.

If students leave gaps between straws or have straws overlapping, have them compare their measurements with another group who had straws of the same length. Consider asking:

• “Why do you think your total number of straws is different?”
• “How did you make sure the entire length of the string was measured?”

• “How long is Priya’s string?”
• Record responses.
• “Why are our length measurements different?” (Some groups maybe didn’t line up their straws correctly. Maybe the straws weren’t the same size.)
• 30 seconds: quiet think time
• 1 minutes: partner discussion
• Share responses.
• Invite previously identified students to demonstrate their measurements.
• “Both of these groups started at the beginning of the string and lined up straws with no gaps or overlaps until they reached the end.”
• “Why are the measurements different?” (The straws are different sizes. One group used short straws and one group used long straws.)
• “The measurements are different because each group used different length units.”
• “A length unit is the length of the object you use to measure.”

The purpose of this activity is for students to understand why it is important to be precise about the length of the unit used to measure (MP6). All student groups use centimeter cubes to measure. After measuring, students compare their measurements with other groups. In the synthesis, they discuss why each group's measurement is the same, or nearly the same, after they measured with the cubes. Students are introduced to standard units, but do not need to use this term.

• Gather a connecting cube to display in the activity synthesis. Students will not need connecting cubes for this activity.

• Groups of 2–3
• Give each group centimeter cubes.
• “In the last activity, we saw why it’s important to use the same length unit to measure. If we use objects as our length unit, we need to all agree on the size of each object.”
• “We are all going to use single base-ten blocks to measure Priya’s string. What do you know about the size and shape of these blocks?” (They are small. They are all the same size. They are cubes.)

• “Your job is to use these cubes to measure the length of the string.”
• 5 minutes: small-group work time
• 5 minutes: small-group discussion

• Share and record measurements.
• “Why is every group's measurements the same, or closer to the same, length?” (They are the same because we all used the same length unit. We all used cubes that have the same length.)
• As needed, restate student responses when they say the cubes are “the same” to emphasize that the cubes have the same length.
• Display a centimeter cube and a connecting cube.
• “If some groups used these cubes and other groups used connecting cubes, would our measurements have been the same? Why?” (It would not be the same because the cubes are not the same length.)
• “Straws and cubes can be confusing to use as length-units because they can be lots of different sizes.”
• “There are units that people around the world use to measure that always have the same size. They are called standard units.”