Use Strategies and Algorithms to Add
The purpose of this lesson is for students to record newly composed tens and hundreds with a single digit and to consider when they might use algorithms or other strategies to add.
In previous lessons, students learned how to use an algorithm that records a single digit for the sum in each place value position, but records 10 or 100 for a newly composed ten or hundred. The purpose of this lesson is for students to continue to work with algorithms, but see that newly composed tens or hundreds can be recorded as a single digit at the top of the tens column or hundreds column. Students also take time to consider when it makes sense to use an algorithm and when it makes sense to use another strategy, such as those learned in grade 2. Students will consider how thinking about the numbers in the problem can help them use their knowledge of addition flexibly to add within 1,000.
- Add within 1,000 using an algorithm or another strategy based on the numbers being added.
- Let’s consider when to use algorithms and when to use other strategies to add.
|Activity 1||15 min|
|Activity 2||20 min|
|Lesson Synthesis||10 min|
Teacher Reflection Questions
What surprised you most about student thinking as they learned how to use algorithms for adding multi-digit numbers?
- Target Numbers (1–5), Stage 6: Add Hundreds, Tens, or Ones (Addressing)
- Five in a Row: Addition and Subtraction (1–2), Stage 8: Add within 1,000 with Composing (Addressing)
- Rectangle Rumble (3–5), Stage 2: Factors 1–5 (Supporting)