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1.1 Variables in Algebra GOAL 1 Evaluate a variable expression.GOAL 2 Write a variable expression that models a real-life situation. What you should learn.

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Presentation on theme: "1.1 Variables in Algebra GOAL 1 Evaluate a variable expression.GOAL 2 Write a variable expression that models a real-life situation. What you should learn."— Presentation transcript:

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2 1.1 Variables in Algebra GOAL 1 Evaluate a variable expression.GOAL 2 Write a variable expression that models a real-life situation. What you should learn To express real-life number relationships. Why you should learn it

3 GOAL 1 EVALUATING VARIABLE EXPRESSIONS VOCABULARY variable values variable expression evaluating an expression 1.1 Variables in Algebra

4 To evaluate a variable expression, follow these three steps: Write the variable expression. Substitute values for variables. Simplify the numerical expression. EXAMPLE 1

5 Extra Example 1 EXAMPLE 2 Evaluate each expression when y = 3. Click for solutions. 1. 4y2.3. y y

6 Extra Example 2 EXAMPLE 3 Find the average speed, of a car that traveled 89 miles in 2 hours. Solution: average speed 44.5 mi/h

7 Extra Example 3 Find the perimeter, a + b + c, of the triangle. The dimensions are in centimeters. Click to see the solution. a = 1 b = 1.75 c = 2.25 Perimeter = a + b + c = = 5 cm

8 Checkpoint 1. Find the average speed of a car that travels 225 miles in 4.5 hours. 50 mi/h 22.7 in 2.Find the perimeter of the triangle. The dimensions are in inches.Click for the answers. c = 6.7a = 8 b = 8 EXAMPLE 4

9 Extra Example 4 Find the simple interest, Prt, you will earn in two years on a deposit of $870 at a rate of 5% per year. Click for the solution. Simple interest = Prt = $87 Did you remember to convert the interest rate to a decimal number? These units cancel.

10 GOAL 2 MODELING A REAL-LIFE SITUATION VOCABULARY Unit Analysis Verbal Model 1.1 Variables in Algebra EXAMPLE 5

11 Extra Example 5 You plan to ride your bicycle to school and back at an average rate of 6 miles per hour for a distance of 10.5 miles. How long will it take you?Click to see the solution. Time = VERBAL MODEL LABELS ALGEBRAIC MODEL Time = t Distance = 10.5 miles Rate = 6 mi/h 1.75 hours

12 Checkpoint 1. Find the simple interest you will earn after one half of a year with a deposit of $1250 at a rate of 6% per year. 2.Your parents drive to the grocery store 9 miles away at 12:30 p.m. and return at 2:00 p.m. If the grocery shopping took 45 minutes, what was the average speed of their car? Click for the answers. $ mi/h

13 QUESTIONS?


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