Lesson objective: Solve problems by using the most efficient computation strategy.

This lesson provides an opportunity for students to apply their knowledge and understanding of addition and subtraction strategies to a real-life situation. Students are asked to use computational strategies to decide which two carnival attractions to ride based on the number of tickets they have to spend.

Key Concept students will use:

Skills students will use:

- Representing and solving an addition/subtraction word problem within 10 (Unit K-10; K.OA.A.2)
- For any number one to nine, there is another number that can be added to it to make 10 (Unit K-12; K.OA.A.4)
- Understanding that the meaning of addition and/or subtraction doesn’t change when different strategies are used (Unit K-10)

Students engage in Mathematical Practice 3 (Construct viable arguments and critique the reasoning of others) as they explain why a certain computation strategy is efficient for the numbers they are adding and subtracting.

**Key vocabulary: **

- addition strategies
- counting on
- making a ten
- open number line
- related facts

**Special materials needed:**

- counters or interlocking cubes
- number line 0-20