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 activity is for students to find the value of differences within 10. Students are encouraged to think about how patterns in subtraction problems and knowing sums within 10 can help them find the value of the differences. Students may use take away or counting on methods. The problems are written for students to think about different methods for solving. For example, students may find the value of
\(10 - 3\)
by taking away 3 to get 7, then see that they can find
\(10 - 7\)
by knowing the relationship between 3, 7, and 10. Students should work in groups of 2, with a different partner than they had in the previous activity.
Engagement: Provide Access by Recruiting Interest.
Provide choice. Invite students to decide which problem to start with.
Supports accessibility for: Social-Emotional Functioning, Attention
Required Materials
Materials to Gather
Connecting cubes or two-color counters
Launch
Groups of 2
Give students access to connecting cubes or two-color counters.
Activity
Read the task statement.
“You will first find the value of each difference on your own. Then you will share your thinking with a different partner than last activity.”
5 minutes: independent work time
2 minutes: partner discussion
Student Facing
Find the value of each difference.
\(9 - 6\)
\(10 - 3\)
\(7 - 3\)
\(9 - 5\)
\(8 - 6\)
\(6 - 5\)
\(9 - 4\)
\(10 - 7\)
Student Response
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Activity Synthesis
“Were there any expressions that helped you with another expression? How did they help you?” (
\(10 - 3\)
and
\(10 - 7\)
. They are related because
\(3 + 7 = 10\)
.
\(9 - 6\)
,
\(9 - 5\)
, and
\(9 - 4\)
. There is a pattern. Since the number being subtracted gets 1 bigger, the difference gets 1 smaller.)


aligns: no