Lesson objective: Add and subtract three-digit numbers without regrouping.

This lesson provides an opportunity for students to apply their knowledge and understanding of three-digit addition and subtraction without regrouping to a mathematical situation. Students are asked to check the correctness of Brian's answers to a three-digit addition and subtraction problem by applying other strategies or tools.

Key Concept students will use: Addition and subtraction strategies used with two-digit numbers can be used with three-digit numbers (no regrouping).

Skills students will use:

- Add numbers within 1,000 using knowledge of place value and properties of operations
- Add numbers within 100 using knowledge of place value (Grade 2, Unit 1)
- Represent three-digit numbers in different but equivalent ways (Grade 2, Unit 6)

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they apply different strategies to solve three-digit addition and subtraction problems, including the use of multiple tools such as base ten blocks and number lines.

**Key vocabulary: **

- base ten blocks
- decompose
- digit
- hundreds
- number line
- ones
- place value
- tens