Lesson objective: Understand that taking from a total is a way to model subtraction.

Students bring prior knowledge of adding to a number from previous experience with K.OA.A.1 and K.OA.A.2. This prior knowledge is extended to contrast the new concept of subtraction as students learn that number can both be added to and alternatively taken from. A conceptual challenge students may encounter is thinking that variations in spatial arrangements or size of objects affects the number of objects remaining in the set after others have been removed.

The concept is developed through work with drawings and a number path, which contrast the orginal set with the remaining amount after some is removed.

This work helps students deepen their understanding of operations because separating and removal situations can be compared and contrasted to combining situations to discover how a total is related to its smaller parts.

Students engage in Mathematical Practice 8 (Look for and make use of structure) as they begin to form deep connections to the structure of a whole set when part is removed. Students notice the remaining set is decreased as the set that is taken from the total increases.

**Key vocabulary:**

- left
- subtract
- subtraction
- take from
- total

**Special materials needed:**

- connecting cubes or counters
- number path
- record sheet (or other tool to record thinking)