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PRE-ALGEBRA Lesson 1-3 Warm-Up PRE-ALGEBRA Writing and Evaluating Expressions (1-3) How do you evaluate an algebraic expression? To evaluate an algebraic expression, replace the varaibles (letters) with the numbers they equal and solve using PEMDAS. Example: Evaluate 4y - 15 for y = 9 4 (9) - 15 36 - 15 Step 1: Replace the variable with the number equals. Step 2: Solve using order of operations [PEMDAS] 21 Example: Evaluate 3ab + c /2 for a =2, b = 5, and c = 10 3(2)(5) + 10 / 2 Step 1: Replace the variable with the number it equals. 30 + 5 Step 2: Solve using order of operations [PEMDAS] 35 PRE-ALGEBRA Writing and Evaluating Expressions LESSON 1-3 Additional Example Evaluate 18 + 2g for g = 3. 18 + 2g = 18 + 2(3) Replace g with 3. = 18 + 6 Multiply. = 24 Add. PRE-ALGEBRA Writing and Evaluating Expressions LESSON 1-3 Additional Example Evaluate 2ab – c for a = 3, b = 4, and c = 9. 3 2ab – c = 2(3)(4) – (9) Replace the variables. 3 3 = = 24 – 3 21 Multiply and divide from left to right. Subtract PRE-ALGEBRA Writing and Evaluating Expressions (1-3) Example: An online store charges $14 for each CD and $6 per order. How much would it cost to order 8 CDs? Number of CD s 1 2 4 8 Cost of CD s 1 x 14 2 x 14 4 x 14 8 x 14 Shipping 6 6 6 6 Total Cost 1 x 14 + 6 = 14 + 6 = 20 2 x 14 + 6 = 28 + 6 = 34 4 x 14 + 6 = 56 + 6 = 62 8 x 14 + 6 = 112 + 6 = 118 Step 1: Create a table to find the pattern (see above). n x 14 + 6 Step 2: Write an expression using the pattern (8) x 14 + 6 Step 3: Replace the variable with the number it equals 112 + 6 Step 4: Solve using order of operations [PEMDAS] 118 PRE-ALGEBRA Writing and Evaluating Expressions LESSON 1-3 Additional Example The Omelet Café buys cases of 36 oranges. a. b. a. x oranges Write an algebraic expression for the number of cases the Café should buy for x oranges. Evaluate the expression for 180 oranges. x 36 b. 180 oranges x (180) = 36 36 = 5 Evaluate for x = 180. Divide. The Omelet Café should buy 5 cases to get 180 oranges. PRE-ALGEBRA Writing and Evaluating Expressions LESSON 1-3 Additional Example The One Pizza restaurant makes only one kind of pizza, which costs $16. The delivery charge is $2 per delivery. Write an algebraic expression for the cost of having pizzas delivered. Evaluate the expression to find the cost of having two pizzas delivered. Words $16 for each Let p Expression 16 pizza plus $2 delivery charge + 2 = number of pizzas. • p Evaluate the expression for p = 2. 16 • p + 2 = 16 • (2) + 2 = 32 + 2 = 34 It costs $34 to have two pizzas delivered. PRE-ALGEBRA Writing and Evaluating Expressions LESSON 1-3 Lesson Quiz Evaluate. 1. 7(b) – 4 for b = 3 17 3. 3c + 4 ÷ d for c = 8, d = 2 26 2. h ÷ 2 + 1 for h = 12 7 4. fg – g for f = 5, g = 7 28 5. Pens are sold at the school store in packages of 4. Write an algebraic expression for the number of packages a student should buy to get p pens. Evaluate this expression for 12 pens. p 12 ; = 3 packages 4 4 PRE-ALGEBRA