 # Addition and Subtraction Within 1000: Partial Sums, Decomposing, Counting Up, and Open Number Lines

3rd Grade • Half Day Lesson Plan
\$6

## Lesson Plan Description

Third Grade half day of math lesson plans containing 3 separate segments (30-60 minutes each) addressing Numbers in Base-Ten: adding and subtracting within 1000 (3.NBT.2). These lessons include: key vocabulary/terms, helpful student notes for reference, guided and independent practice of addition and subtraction methods (partial sums, decomposing, counting up, and open number lines), and a game to reinforce the concept of adding and subtracting within 1000 using an open number line.

• Segment 1: students will use expanded form to decompose a number and identify the value of the digits. They will use this knowledge to add using the partial sums method and subtract using the decomposing method.
• Segment 2: students will add and subtract within 1000 using open number lines.
• Segment 3: students will reinforce their knowledge of the value of digits and place values by adding and subtracting within 1000 using open number lines.

These lessons can be taught over the span of a half day or you can use the lessons independently, broken up over several days.