1. 1.1 Variables in Algebra August 27, 2008 Warm-up : Write the following question in the warm-up section of your daily sheet, then answer the question If you take half of ten from seven, what do you have?

2. Outcomes YWBAT: Evaluate a Variable Expression Write a variable expression that models a real-life situation Evaluate a geometric expression Find simple interest using the simple interest formula

3. VOCABULARY Variable Values Variable expression Evaluate Verbal model

4. List things that vary What does it mean to vary?

5. Def: Variable Def: Variable Expression

6. Def: Value Def: Evaluate

7. Evaluating a Variable Expression When you evaluate a variable expression, you find the value of an expression after replacing the variable

8. Example: Find the value of each variable expression when x = 4 1. x 2 2. –x 2 3. (-x) 2 4. 25 – 3y

9. Evaluating a Real-life Expression The average speed of a race car in the Indianapolis 500 race is 500 miles divided by the number of hours the race takes. For example, in 1997, the average speed of the winning car was 500 miles/3.4 hours, or about 147 miles per hour. What formula could we use to represent average speed ?

10. Find the average speed of a car that travels 225 miles in 4.5 hours

11. Evaluating a Geometric Expression How do we find the perimeter of a triangle? Ex. Find the perimeter of the triangle a = 1 b = 1.75 c = 2.25

12. Evaluating Simple Interest Simple Interest? Formula?

13. How much simple interest will be earned if $500 is invested at 6% interest for 10 years?

14. Modeling a Real-Life Situation You plan to ride your bicycle to school and back at an average rate of 6 mph for a distance of 10.5 miles How long will it take you?

15. Guided Practice: In your notebook, write each problem and simplify. When you are finished, have your answers checked by me, Marissa or Kristie 1.Evaluate each expression when y = 3 a. 4yc. y + 8 b. 12/y d. 18 – y 2.Find the average speed of a car that traveled 89 miles in 2 hours. 3.Find the perimeter of the triangle on the back board 4.Find the simple interest Prt, you will earn in two years on a deposit of $870 at a rate of 5% per year. 5.Your parents drive to the grocery store 9 miles away at 12:30 PM and return at 2:00 PM If the grocery shopping took 45 minutes, what was the average speed of their car?