The purpose of this Warm-up is to elicit what students know about length measurement and about units of measurement. While no unit is specified for the ruler in the image, students are likely to bring up centimeters (given the way each 1 unit is partitioned into 10 smaller parts, as seen on centimeter rulers). The work here prepares students to think about the relationship between meters and centimeters later in the lesson.

• Consider sharing that the large insect is a stick insect. (The longest species of stick insect ever found measured more than 60 cm.) The small insect is a green potato bug.
• “If each unit in the ruler is 1 centimeter, about how long is the potato bug?” (1 cm) “What about the stick insect?” (About 16 cm with the antennae, about 12 cm otherwise.)

• “How did you organize and count the centimeter pieces?”
• “How can you make sure there are 100 centimeter pieces?”

• "How did you decide whether Priya's measurements in centimeters were correct or not?"
• "How could you use the strips we made to explain why this happens?"