Lesson 5
Subtract Your Way
Lesson Purpose
Lesson Narrative
In grade 1, students added within 100 using strategies based on place value and properties of operations. When using place value strategies to add, students learned that sometimes they need to compose a ten. To this point, when subtracting within 20, students used methods like counting on, decomposing a number to get to a ten, and using known addition facts, but did not explicitly decompose a ten.
In this lesson, students subtract a onedigit number from a twodigit number when a ten would need to be decomposed if they subtract by place. When subtracting a onedigit number from a twodigit number, students may count back to get to a ten and then count back from there. Although subtracting or counting back in this way is an effective method when subtracting a singledigit number, it is less practical when subtracting twodigit numbers. For this reason, students are encouraged to use cubes and baseten blocks to help make decomposing a ten visible to all students and prepare students to consider decomposing the minuend in order to subtract by place. For example, \(26 = 10 + 16\), so decomposing 26 into 1 ten and 16 ones will be helpful when representing subtraction using baseten blocks later in this lesson.
 Representation
 MLR8
Activity 2: Subtract with Baseten Blocks
Learning Goals
Teacher Facing
 Subtract a onedigit number from a twodigit number in a way that makes sense to them.
Student Facing
 Let’s subtract onedigit numbers from twodigit numbers.
Required Materials
Materials to Gather
Required Preparation
Lesson Timeline
Warmup  10 min 
Activity 1  20 min 
Activity 2  15 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
Suggested Centers
 Capture Squares (1–3), Stage 3: Add within 20 (Addressing)
 Five in a Row: Addition and Subtraction (1–2), Stage 6: Add within 100 with Composing (Addressing)
Print Formatted Materials
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Additional Resources
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