Lesson objective: Practice explaining the comparison between known quantities and an unknown value.

This lesson helps to build fluency with comparison statements. Number lines are used here because they allow students to compare two-digit numbers and see the distance between these numbers using a visual model. This work develops students' understanding that we can compare known quantities by the unknown value.

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they notice that they can use the properties of operations and the relationship between addition and subtraction to solve comparison situations using the number line. Students also engage in Mathemaptical Practice 7 (Look for and make use of structure) as they utilize their knowledge of number sequence when comparing two numbers using “more” and “less" than.

**Key vocabulary:**

- addend
- addition
- between
- compare
- comparison
- comparison statement
- distance
- equation
- greater than
- less
- less than
- missing number
- more
- number line
- sequence
- subtraction
- tape diagram
- two-digit number
- unknown number
- visual model

**Special materials needed:**

- game cards
- white boards/markers or paper/pencil