standard_description: Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.
problem_activity: Narrative
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).
Required Materials
Materials to Gather
Base-ten blocks
Launch
Groups of 2
Display the image.
“What do you notice? What do you wonder?”
1 minute: quiet think time
Activity
“Discuss your thinking with your partner.”
1 minute: partner discussion
Share and record responses.
Student Facing
What do you notice? What do you wonder?
A
[IMG]
B
[IMG]
Student Response
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Activity Synthesis
“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.”


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