In previous grades, students developed fluency with sums of 10 and looked for ways to make a ten as a strategy for adding within 20. They used their understanding of these sums to make sense of composing a ten when adding by place and as a strategy for adding within 100.
In this lesson, students use what they know about making a ten to find the sum of a three-digit number and a two-digit number. Throughout the lesson, students may use the methods that make the most sense to them to add which may include counting or adding-on by place or adding tens and tens and ones and ones. They may also use whichever representations help them make sense of each sum, including number lines or base-ten blocks. The activity and lesson syntheses focus on using known sums of 10 to anticipate when a ten is composed when adding by place. This understanding will be used in upcoming lessons as students add two three-digit numbers by place and anticipate when units may need to be composed.
- Action and Expression
- Add numbers within 1,000 using place value strategies that include composing a ten.
- Let’s add three-digit numbers by composing a ten.
Materials to Gather
Materials to Copy
- Card Sort Perfect 10
- Create a set of cards from the blackline master for each group of 3.
|Activity 1||15 min|
|Activity 2||20 min|
|Lesson Synthesis||10 min|
Teacher Reflection Questions
- Five in a Row: Addition and Subtraction (1–2), Stage 7: Add within 1,000 without Composing (Addressing)
- How Close? (1–5), Stage 3: Add to 100 (Supporting)
Print Formatted Materials
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