Lesson objective: Solve problems using a number line to show addition and subtraction methods for solving one step liquid volume problems.

This lesson provides an opportunity for students to apply their knowledge and understanding of adding and subtracting milliliters to a real-life situation. Students are asked to show their method for solving liquid volume problems on the number line.

Key Concept students will use:

Skills students will use:

- a number line to solve many types of addition and subtraction problems (Grade 2, Unit3, Unit 8)
- compose or decompose tens or hundreds when adding or subracting three-digit numbers (Grade 2, Unit 11)
- place value understanding to add and subtract using a variety of strategies (Grade 3, Unit 3).

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them)** **as they use the number line and pictures to show their methods for adding and subtracting to solve liquid volume problems. Students engage in Mathematical Practice 4 (Model with mathematics) as they write number equations to explain their methods for solving the problem.

**Key vocabulary: **

- liters
- liquid volume
- milliliters
- number line

**Special materials needed:**

- base ten blocks- units, rods, flats, blocks
- number line for demonstrating placement of numbers between 100's