standard_description: Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
problem_activity: Narrative
The purpose of this Estimation Exploration is to practice the skill of estimating a reasonable answer based on experience and known information.
Launch
Groups of 2
Display the image.
“What is an estimate that’s too high?” “Too low?” “About right?”
1 minute: quiet think time
Activity
“Discuss your thinking with your partner.”
1 minute: partner discussion
Student Facing
How many cranes are there in the image?
[IMG]
Record an estimate that is:
|                    too low                     |                  about right                   |                    too high                    |
|------------------------------------------------|------------------------------------------------|------------------------------------------------|
| \(\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}\) | \(\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}\) | \(\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}\) |
Student Response
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Activity Synthesis
“Is anyone’s estimate less than 20? Is anyone’s estimate greater than 30?”
“Based on this discussion does anyone want to revise their estimate?”


aligns: no