Lesson objective: Practice using knowledge of place-value to comparing two-digit numbers.

This lesson provides an opportunity for students to practice using their understanding of place-value to a mathematical situation. Students are asked to play a game wherein they figure out a mystery number through the use of comparison and deductive reasoning.

Key Concept students will use:

- Understanding the structure of the place value system allows us to determine whether one number within 99 is greater than, less than, or equal to another number.

Skills students will use:

- Knowledge of place-value.
- Knowledge of comparison (Grade K, Unit 14).

Students engage in Mathematical Practice 2 (students make sense of the relationship between the numericals and the quantities; students will notice the pattern in the numericals as the quantities those numbers represent change) as they compare two-digit numbers to discover their partner's mystery number.

**Key vocabulary: **

- between
- equal to
- greater than
- less than

**Special materials needed:**

- game cards
- base ten blocks