standard_description: Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.
problem_activity: Narrative
The purpose of this activity is for students to use what they know about making a ten to identify which addition expressions are equivalent to
\(10 + n\)
expressions. Students should have access to double 10-frames and connecting cubes or two-color counters.
The Compare Stage 2 Addition Cards will be used again in a later lesson.
Required Materials
Materials to Gather
Connecting cubes or two-color counters
Double 10-frames
Materials to Copy
Compare Stage 2 Addition Cards to 20
Required Preparation
Create a set of Compare Stage 2 Addition Cards to 20 from the blackline master for each group of 3.
Launch
Groups of 3
Give each group a set of cards and access to double 10-frames and connecting cubes or two-color counters.
Activity
Read the task statement.
8 minutes: small-group work
Student Facing
Take out all the expression cards that have the number 10.
Mix up the rest of the cards.
Pick a card.
Place the card under the expression with 10 that it is equal to.
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Student Response
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Activity Synthesis
“We are going to create a poster and do a Gallery Walk.”


aligns: no