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Writing & Evaluating Variable Expressions. Chapter 1-3 Pre-Algebra Prentice Hall. Evaluation Variable Expressions. To evaluate a variable expression, you first replace each variable with a number. Than, you use the order of operations to simplify the expression.
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Writing & EvaluatingVariable Expressions Chapter 1-3 Pre-Algebra Prentice Hall
Evaluation Variable Expressions • To evaluate a variable expression, you first replace each variable with a number. Than, you use the order of operations to simplify the expression. • Evaluate: 4y − 15 for y = 9 • First replace the variable y with number 9 • 4∙9 − 15 • Than use order of operation to simplify: • 36 − 15 = 21
Quick Check • Evaluate each expression. • 6(g + h), for g = 8 and h =7 • 90 • 2xy – z, for x = 4, y = 3, z = 1 • 23 • for r = 13, and s = 11 • 12
Purchasing Problem Example • Energy drinks come in cases of 24 bottles. • Write a variable expression for the number of cases a store should order to get b bottles of energy drinks. • Evaluate the expression for 120 bottles. ← bottles wanted ← number in case Evaluate for b = 120 cases
Exercises • 15 • 11 • 91 • 99 • 2
Problems • Write an expression for the number of kilometers a dolphin travels in d hours swimming at 8km/h. Then find the number of kilometers the dolphin travels in 3 hours • 8d 24 km • A fitness club requires a $100 initiation fee and dues of $25 each month. Write an expression for the cost of membership for n months. Then find the cost of membership for one year. • 100 + 25n $400
