Objective: Students will be able to add two two-digit numbers within the range of 0 to 20 correctly.

Materials: - Blank paper - Pencils - Whiteboard

Lesson:

1. Introduction (10 minutes): To introduce this lesson, explain to the students the importance of being able to add two two-digit numbers within 20. Ask them for examples of situations where this ability could come in handy (such as going to the store, keeping track of a budget, etc.).

2. Modeling (15 minutes): Using the whiteboard, demonstrate the process of adding two two-digit numbers within 20. Model the steps using real numbers, such as 16 + 19. Explain the importance of regrouping numbers when necessary.

3. Practice Activity (30 minutes): Distribute the blank paper and pencils to the students. Have them practice the process of adding two two-digit numbers on their own to further engrain the skill. Give them guidance as needed. Once they have finished their practice activity, have them turn in their answers so that you can check for understanding.

4. Closure (5 minutes): Have the students summarize what they have learned in this lesson. Ask them to explain the process they used when adding two two-digit numbers. This will give them an opportunity to demonstrate their understanding of what was taught during the lesson.