Lesson objective: Relate the relationship between addition and subtraction to choose the most efficient strategy to solve a word problem.

This lesson provides an opportunity for students to apply their knowledge and understanding of the relationship between addtion and subtraction to a real-life situation. Students are asked to purchase beads to make bracelets. They must choose at least three colors of beads to buy from a table that includes color and number of beads. They must buy between 850 and 900 beads.

Key Concept students will use:

- We can use the relationship between addition and subtraction to add and subtract within 1000.

Skills students will use:

- Estimation
- Understanding addition and subtraction as inverse operations
- Place value strategies for addition and subtraction

Students engage in Mathematical Practice 2 (Reason abstractly and quantitatively) as they create logical representations of the problem at hand and use what they know about the relationship between addition and subtraction to choose which operation would be the most efficient.

**Key vocabulary: **

- addition
- estimation
- inverse operations
- open number line
- subtraction