# 7. Understand that the value of 10 does not change regardless of how it is composed (C)

teaches Common Core State Standards CCSS.Math.Content.K.OA.A.4 http://corestandards.org/Math/Content/K/OA/A/4
teaches Common Core State Standards CCSS.Math.Practice.MP8 http://corestandards.org/Math/Practice/MP8

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Lesson objective: Understand that the value of 10 does not change regardless of how it is composed.

Students bring prior knowledge of composing and decomposing numbers from K.OA.3. This prior knowledge is extended to composing and decomposing 10 as students find all of the combinations of numbers one to nine that compose 10. A conceptual challenge students may encounter is thinking that the total value changes as different numbers are paired to compose 10.

The concept is developed through work with a 10-strip and 10 two-sided counters, which structure the counting and help students track the total of 10 objects while also visualizing different combinations to compose 10. They help students see that the total quantity of objects does not change even as the combinations that compose the total change.

This work helps students deepen their understanding of equivalence because students develop the understanding that the value of 10 does not change regardless of how it is composed.

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they analyze patterns to find all of the combinations that make 10.

Key vocabulary:

• compose
• decompose
• make a 10
• number bond
• number partner
• 10-frame
• total

Special materials needed:

• 10-frames
• 10-strips
• two-sided counters (commercial or painted lima beans)
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