Lesson objective: Understand how to count up and make a ten as strategies to add within 20.

Students bring prior knowledge of adding within 10 from K.OA.A.2, "Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem." This prior knowledge is extended to strategies to add within 20 as students interact with a cafeteria table context that utilizes the strategies of counting on and making a ten. A conceptual challenge students may encounter is counting on from a given number. Students may still want to start back at 1 instead of counting on.

The concept is developed through work with a real-life context of cafeteria tables and with a number path, which allow studetns to see a group of ten for making a ten and for seeing the linear path of numbers when counting on.

This work helps students deepen their understanding of operations because counting on and making a ten are foundational strageties used by students in computation with small and larger numbers.

Students engage in Mathematical Practice #2, reason abstractly and quantitativley as they work with a real-life context of cafeteria tables and students sitting at the tables. Students will move between the real-life context represting quantities of students and tables to using a number path to represent the same information. They will see representation of the context of students joining tables using a number sentence.

**Key vocabulary:**

- add
- combinations
- counting on
- make a ten
- sum
- total

**Special materials needed:**

Items below are not required, but should be provided to students to help solve the task.

- tens frames
- counters
- number path 0 -20