# Lesson 1

Inputs and Outputs

### Lesson Narrative

This is the first of two lessons introducing students to functions, developing the idea of a function as a rule that assigns to each allowable input exactly one output. The word function is not introduced until the second lesson. In future lessons, students will expand on this definition as they work with different representations of functions.

In the first classroom activity students take turns guessing each other's rules from input-output pairs. In the second activity students use rules represented by input-output diagrams to fill out a table with inputs and associated outputs. In each table, the first input-output pair is identical, illustrating that a single pair is insufficient for determining a rule. The last table returns to the topic of the warm-up and introduces the idea that not all inputs are possible for a rule.

### Learning Goals

Teacher Facing

• Describe (orally) how input-output diagrams represent rules.
• Identify a rule that describes the relationship between input-output pairs and explain (orally) a strategy used for figuring out the rule.

### Student Facing

Let’s make some rules.

### Required Preparation

Print and cut up slips from the Guess my Rule blackline master. Prepare 1 copy for every 4 students. During the activity, you will want students to place the slips in a pile, face down, with rule A on top and rule D on the bottom.

### Student Facing

• I can write rules when I know input-output pairs.
• I know how an input-output diagram represents a rule.