2.  Lesson Objective: NCSCOS 4.01 Use linear functions to model and solve problems; justify results.  Students will know how to write an equation from a problem.  Students will know how to solve equations for a variable.

3.  Tamara charges $25 per hour to clean windows. She also receives $5 for transportation to the job. One Saturday, Tamara earned $130.  The first step to solving a problem like this is to find the question.  What is the question asking for?  If we don’t know something what do we call it? How many hours did Tamara work?

4.  Tamara charges to clean windows. She also receives $5 for transportation to the job. One Saturday, Tamara earned $130. How many hours did Tamara work?  We know that hours =  What goes with hours in the problem?  $25 $25 per hour

5.  Start with the equation of a line:  We know that $25 goes with the x, so plug it in for m.  We now have to replace the “b” to get our equation

6.  Tamara charges $25 per hour to clean windows. She also receives for transportation to the job. One Saturday, Tamara earned $130. How many hours did Tamara work?  “b” is the y-intercept or the constant so it doesn’t change  How much does Tamara make no matter how long she works? $5

7.  Replace the “b” with $5:  always represents a total. If there is a total in the problem, we will replace the y with the total

8.  Tamara charges $25 per hour to clean windows. She also receives $5 for transportation to the job. One Saturday, How many hours did Tamara work?  Is there a total?  Therefore, y = $130 Tamara earned $130.

9.  Replace y with $130  Solve for x: subtract 5 from both sides  Divide both sides by 25

10.  An MP3 player costs $195 including tax. You already have $37 and can save $9 per week. After how many weeks can you buy the player?

11.  An MP3 player costs $195 including tax. You already have $37 and can save per week. After how many can you buy the player?  Write the equation of a line  What is the question asking for?  x = # of weeks  What goes with the # of weeks? weeks $9

12.  An MP3 player costs $195 including tax. You already have $37 and can save $9 per week. After how many can you buy the player?  Replace m with $9  $37 doesn’t change since you already have that in the bank. Replace b with $37  $195 is the total, so replace y with $195 weeks

13.  Subtract 37 from both sides  Divide both sides by 9  If the number of weeks isn’t an even number, round up

14.  An MP3 player costs $195 including tax. You already have $37 and can save $9 per week. After how many weeks can you buy the player?  In 18 weeks you will have enough for the Mp3 player

15.  A telephone calling card allows 25¢ per minute plus a one-time service charge of 75¢. How many minutes can Rob talk if he paid $5 for the card?

16.  The Brown’s computer repair bill was $225. This included $75 for parts and $50 for each hour of labor. How many hours did the computer repairman work?  A local airport charges $12 for the first day of parking and $9 for each additional day. Gus paid $120 for parking. How many days was Gus’s car parked at the airport?