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1.1 Variables in Algebra

1.1 Variables in Algebra. How many miles has the bike traveled ? A racing biker travels down the road at 35 miles per hour. How many miles will the bike travel in 3 hours?. Objectives : to write and evaluate variable expressions. Try the warm-up exercise Definitions: Variable -

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1.1 Variables in Algebra

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  1. 1.1 Variables in Algebra How many miles has the bike traveled? A racing biker travels down the road at 35 miles per hour. How many miles will the bike travel in 3 hours?

  2. Objectives: to write and evaluate variable expressions • Try the warm-up exercise • Definitions: • Variable - • a letter that is used to represent a • range of numbers. (ex. n, x, y) • For Example: We can let the letter n represent • the number we chose to begin the • warm-up exercise. • Variable expression - • expressions that consist of • variables, constants, and math • operations. • Ex. 8y, 4 + x, 16 • b

  3. Example 1: Describe the variable expression • Variable expressionMeaningOperation • 3x, 3 • x, (3)(x) __times__ Multiplication • 14 , 14÷y 14_______y Division y • 9 + a 9________a Addition • 12 – b 12_______b Subtraction Example 2: Write a variable expression • Eight more than a number n + 8 b. Five less than a number n – 5 c. A number divided by 3 n/3 or n ÷ 3 • Five more than three times a number 3n + 5

  4. Can you now write a variable expression for our warm-up exercise? 2(n + 5) – 2n – 10 • Example 3: Evaluate (solve) the variable expression • When x = 5 • Expression a.) 5x b.) 40 x Substitute 5 • 5 40 5 • Simplify 25 8 Example 4: Evaluate rt to find distance (d = rt) Find the distance (d) of our biker who rode 3 hours (t time in hours) and went an average speed of 35 miles per hour (r rate). Solution: d = (35)(3) d = 105 miles (What if the time changes to 30 minutes?)

  5. Review vocabulary: • Perimeter - • the distance around a polygon • (note: add together the length of the sides) • Area - • the space inside a closed geometric shape • (note: use a formula to calculate area) • A(triangle) = bh A(rectangle) = lw • 2 • In Class: Pg. 6 #1-4, 6-16 • Homework: Pgs. 6-8 #17-27, 34-37, 50-60even • Extra credit: (5 points) #40, 43, 46, 51

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