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Lesson 3-5: Introduction to Functions

Scenario: Transportation Costs - Learn the basics of functions through taxi fare calculations!

Duration: 60-75 minutesScenario: Transportation Costs

Learning Objectives

  • Understand what a function is and how it works
  • Create and use function tables
  • Identify input-output relationships
  • Apply functions to real-world transportation scenarios

Taxi Fare Function

The Problem

A taxi charges $3.50 as a base fare plus $2.25 per mile. Create a function to calculate the total cost for any number of miles.

Function: f(x) = 3.50 + 2.25x
Where x = number of miles traveled

What is a Function?

Function Definition: A function is a relationship where each input (x) has exactly one output (f(x)).

Input (x)
Function
Output (y)

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

Function Table

Creating a Function Table

Let's calculate the taxi fare for different distances using f(x) = 3.50 + 2.25x

Miles (x)CalculationTotal Cost f(x)
03.50 + 2.25(0)$3.50
13.50 + 2.25(1)$5.75
23.50 + 2.25(2)$8.00
33.50 + 2.25(3)$10.25
53.50 + 2.25(5)$14.75

Function Applications

Using the Function

Example 1: Find Cost

How much does a 4-mile taxi ride cost?
f(4) = 3.50 + 2.25(4)
f(4) = 3.50 + 9.00 = $12.50

Example 2: Find Distance

If the fare is $20, how far did you travel?
20 = 3.50 + 2.25x
16.50 = 2.25x
x = 7.33 miles

Function Notation

Function Notation: f(x) = 3.50 + 2.25x

  • • f is the name of the function
  • • x is the input variable (miles)
  • • f(x) is the output (total cost)
  • • We can also write y = 3.50 + 2.25x

Practice Problems

Problem 1: Function Evaluation

Using f(x) = 3.50 + 2.25x, find f(6)

Your solution:

Problem 2: Create Function Table

A parking garage charges $2.00 base fee plus $1.50 per hour. Create a function and table for 0, 1, 2, 3, and 4 hours.

Your function and table: