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
In this activity, students solve addition problems using money based on the Pattern Block Puzzles they sketched in the last activity.
The launch of the activity is an opportunity for students to reason which of the two designs will cost more before they complete any computations.
MLR7 Compare and Connect.
Synthesis: After all strategies have been presented, lead a discussion comparing, contrasting, and connecting the different approaches. Ask, “Did anyone solve the problem the same way, but would explain it differently?”, “What did the representations have in common?”, “How were they different?”
Advances: Representing, Conversing
Launch
Groups of 2
“At the Pattern Block Store, each pattern block shape has a different price.”
Display the price list.
“Which of the two puzzles that you sketched do you think will cost more to make? Puzzle 1 or 2?”
30 seconds: quiet think time
1 minute: partner discussion
Share responses.
Activity
“Use the price list to figure out how much your two puzzles would cost.”
5 minutes: independent work time
5 minutes: partner discussion
As students work, look for different addition strategies. Monitor for students who:
add like quantities first
add bigger or smaller coins first
add some coins mentally
Student Facing
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How much would the two puzzles you sketched cost at the Pattern Block Store? Show or explain your reasoning.
Puzzle 1:
Puzzle 2:
Student Response
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Activity Synthesis
Invite previously selected students to share.
“Is it possible to redesign the puzzle to save more money?” (Yes, I can switch a blue rhombus with two triangles.)


aligns: no