22 Chapter 1 The Set of Real Numbers The value of an algebraic expression depends on the values of the variables within the expression. Evaluating an Algebraic Expression Example 1 The expression 220 a represents the maximum recommended heart rate for an adult of age a. Determine the maximum heart rate for: a. A 20-year-old b. A 45-year-old Solution: a. In the expression 220 a, the variable, a, represents the age of the individual. To calculate the maximum recommended heart rate for a 20-year-old, we substitute 20 for a in the expression. 220 a 220 ( ) When substituting a number for a variable, use parentheses. Substitute Subtract. 220 1202 a 20. 200 The maximum recommended heart rate for a 20-year-old is 200 beats per minute. b. When substituting a number for a variable, use parentheses. Substitute Subtract. 220 a 220 1 2 220 1452 a 45. 175 The maximum recommended heart rate for a 45-year-old is 175 beats per minute. Skill Practice 1. After dining out at a restaurant, the recommended minimum amount for tipping the server is 15% of the cost of the meal.This can be represented by the expression 0.15c, where c is the cost of the meal. Compute the tip for a meal that costs: a. $18 b. $46 Evaluating Algebraic Expressions Evaluate the algebraic expression when and a. b. pq Solution: a. When substituting a number for a variable, use parentheses. Substitute in the parentheses. 100 p 100 p 100 1 2 100 142 p 4 96 Subtract. q 34 p 4 . Example 2 Answers 1. a. $2.70 b. $6.90
miller_beginning_intermediate_algebra_4e_ch1_3
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