Lesson objective: Solve a riddle using addition and subtraction strategies.

This lesson provides an opportunity for students to apply their knowledge and understanding of adding and subtracting two-digit numbers to a mathematical situation. Students are asked to use clue cards to determine how many exercises should be completed.

Key Concept students will use:

- Addition and subtraction can be used in many different ways.

Skills students will use:

- adding and subtracting within 20 (e.g., Grade 2, Unit1)

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they determine how each clue card should be solved and choose a strategy to use to add or subtract.

**Key vocabulary: **

- add
- arm circle
- jumping jack
- number line
- sit ups
- subtract