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Lesson 3-5: Function Basics

Scenario: Taxi Fares - Explore function relationships through transportation costs!

Duration: 60-75 minutesScenario: Taxi Fares

Learning Objectives

  • Understand what a function is and how it relates inputs to outputs
  • Create and interpret function tables
  • Write function rules from real-world scenarios
  • Use functions to solve practical problems

Taxi Fare Function

Taxi Pricing

A taxi charges $3 for the first mile and $1.50 for each additional mile. The total fare (y) depends on the number of miles traveled (x).

Function Rule: y = 1.5x + 3

Function Table

Miles (x)CalculationFare (y)
01.5(0) + 3$3.00
11.5(1) + 3$4.50
21.5(2) + 3$6.00
31.5(3) + 3$7.50

What is a Function?

Function Definition

A function is a relationship where each input (x) has exactly one output (y). Think of it as a machine that takes a number and gives you back exactly one result.

Input (x)
Function
Output (y)

Key Rule: For every x, there is exactly one y

More Function Examples

Example 1: Temperature Conversion

Convert Celsius to Fahrenheit: F = 1.8C + 32

Function Table:
C = 0 → F = 32°F
C = 10 → F = 50°F
C = 20 → F = 68°F
C = 30 → F = 86°F

Example 2: Area of Square

Area = side length squared: A = s²

Function Table:
s = 1 → A = 1 square unit
s = 2 → A = 4 square units
s = 3 → A = 9 square units
s = 4 → A = 16 square units

Using Functions to Solve Problems

Reverse Problem

If the taxi fare is $12, how many miles did you travel?

Step 1: Set up the equation

12 = 1.5x + 3

Step 2: Solve for x

12 - 3 = 1.5x
9 = 1.5x
x = 6 miles

Answer: You traveled 6 miles.

Practice Problems

Problem 1

A movie theater charges $8 for adults and $5 for children. Write a function rule for the total cost if a adults and c children attend.

Your function rule:

Problem 2

Using the taxi function y = 1.5x + 3, find the fare for 8 miles and determine how many miles you can travel with $15.

Your solution: