standard_description: Derive the formula for the sum of a finite geometric series (when the common ratio is not 1), and use the formula to solve problems. For example, calculate mortgage payments.
problem_activity: Narrative
The purpose of this lesson is for students to solve a Put Together/Take Apart, Both Addends Unknown story problem in the context of putting together pattern blocks (MP2). If students finish early, invite them to find multiple solutions to the story problem.
MLR8 Discussion Supports.
Synthesis: For each decomposition that is shared, invite students to turn to a partner and restate the recorded equation.
Advances: Listening, Speaking
Required Materials
Materials to Gather
10-frames
Connecting cubes or two-color counters
Pattern blocks
Launch
Groups of 2
Give students access to connecting cubes or two-color counters, 10-frames, and pattern blocks.
Read and display the task statement.
“Tell your partner what happened in the story.”
30 seconds: quiet think time
1 minute: partner discussion
Monitor for students who accurately retell the story. Choose at least one student to share with the class.
Reread the task statement.
“Show your thinking using drawings, numbers, words, or objects.”
Activity
2 minutes: independent work time
2 minutes: partner discussion
“If you haven’t already, write an expression to show how many square pattern blocks and triangle pattern blocks Diego used.”
2 minutes: independent work time
Student Facing
Diego built a shape with 10 pattern blocks.
He only used squares and triangles.
How many square pattern blocks did Diego use?
Then how many triangle pattern blocks did Diego use?
Expression: _________________________________
Student Response
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Activity Synthesis
Invite students who found different decompositions of 10 to share.
As students share, record each solution with an equation, such as
\(10 = 7 + 3\)
.
“Did _____ and _____ both show what happened in the story? How do you know?” (Yes. They both have 10 pattern blocks, with some triangles and some squares.)
“In the next activity, we will find more ways that we can make shapes with 10 pattern blocks.”


aligns: no