Variables and Expressions September 21, 2009

Warm up Spiral Review and Test Prep 1-13Show your work. 1. Evaluate Belinda borrowed $137 from her parents. She is planning to pay her parents $20 a week. How many weeks will it take Belinda to pay for her lessons? 2. Round to the nearest ten million. 348,298, Fill in the blank and tell the property the problem shows. (8 x 6) ___ = 8 x (6 x5) 3. (14-6) x (6-3)+14/2=7. Mia biked the 9-mile trail and then the 15-mile trail. Josef biked the 15-mile trail and then the 9-mile trail. Using one of the properties, write a number sentence to show that each traveled the same distance. 4. Divide. 234/9 8. Fill in the blank (10 + 6)20 = 10(20) + 6(___)

Variables Nita bought some candles costing $4 each. How can you represent their total cost? Make a table to show the cost for different quantities of candles. Use a letter such as n to represent the number of candles. Because n represents a quantity whose value can vary, it is called a variable. The total cost of the candles is represented by 4 x n or 4n.

Table Number of CandlesTotal Cost ($) 14 x 1 24 x 2 34x 3 44 x 4 N (any number)4x n

Algebraic Expressions An algebraic expression is a mathematical expression containing variables, numbers, and operation symbols. Before you write an algebraic expression, identify the operation. The table below shows how two or more word phrases can refer to an operation.

Word PhraseOperationAlgebraic Expression the sum of 9 and a number n Addition9 + n the difference of 12 and a number n Subtraction12 - n the product of 4 and a number k Multiplication4k4k the quotient of a number divided by five Divisiona5a5

Practice Write each word phrase as an algebraic expression. 1) 25 more than p________ 2) the product of s and 7_______ 3) 14 decreased by e________4) n divided by 18__________ Evaluate each expression for b 6. 5) b x 5=_______ 6) 19 + b_________ 7) 42 / b___________ For 8–11, evaluate each expression for n 3, 5, and 7. 8) n -1___,____,____ 9) n + 13____,_____,______ 10) 9n____,_____,_____ /n_____,______,______

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