1. 4-2 Writing Equations given Word Problems
Goal:
Use a linear equation to model a real-life problem.
Eligible Content:
A / A / A / A / A / A / A

2. Word Problems Slope still means rate of change (y per x).
y-intercept still means beginning amount.
Ordered pairs are created by pairing up numbers that go together.

3. Word Problem #1
Billy is charged $50 to rent a car for the week. He also has to pay $.25 per mile.
Slope is $ per mile
Write a linear equation that models this situation.
y = .25x + 50
Use your equation to find the charge for 75 miles.
$68.75

4. Word Problem #2
Wanda hires someone to fix her heater. She is told that she will be charged a base fee and $45 per hour. Her bill is $215 and it took 2 hours to fix her heater.
Slope is $ per hour
Write a linear equation that models this situation.
y = 45x + 125
Use your equation to find the charge for 3.5 hours.
$282.50

5. Word Problem #3
A camp program charges a registration fee and a daily amount. The total bill for 12 days is $338. The total bill for 19 days is $506.
Slope is $ per day
Write a linear equation that models this situation.
y = 24x + 50
Use your equation to find the charge for 30 days.
$770

6. Word Problem #4
A baseball player was keeping track of the number of runs he batted in after each game. After 21 games, he had 45 runs batted in. After 84 games, he had 87 runs batted in.
Slope is runs per game.
Write a linear equation that models this situation.
y = x + 31
Use your equation to find the number of runs batted in after 102 games.
99 runs

7. Slope is flights per year
Word Problem #5
In 2004, there were 9.97 million domestic flights in the US. In 2008, there were 9.37 million domestic flights. Let x = 0 correspond to 2000.
Slope is flights per year
Write a linear equation that models this situation.
y = –0.15x
Use your equation to find the number of domestic flights in
8.62 million flights

8. The cost of a textbook that Mrs. Lambert uses in her class was $57
The cost of a textbook that Mrs. Lambert uses in her class was $57.65 in She ordered more books in and the price increased to $ Write a linear equation to estimate the cost of a textbook. Let x represent years since 2005.
A. y = 3.5x
B. y = 3.5x
C. y = 57.65x
D. y = –3.5x – 10

9. Practice
Worksheet – “4-2 Word Problems”

10. Homework
Pages #24, 31, 32, 40, 41, 42
Do not graph!