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Check it out!. 2.1.2: Solving Linear Equations. The cost C of mailing a letter first class in the United States is $0.45 for the first ounce. Each added ounce, or fraction of an ounce, costs an additional $0.20.

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  1. Check it out! 2.1.2: Solving Linear Equations

  2. The cost C of mailing a letter first class in the United States is $0.45 for the first ounce. Each added ounce, or fraction of an ounce, costs an additional $0.20. Write an equation to represent the total cost, C, to mail a first class letter that weighs n ounces. How much does it cost to mail a letter that weighs 3.2 ounces? How much does a letter weigh if it costs $1.85 to mail it? 2.1.2: Solving Linear Equations

  3. Write an equation to represent the total cost, C, to mail a first class letter that weighs n ounces. The equation that represents the total cost, C, is C = 0.45 + 0.20(n – 1). 2.1.2: Solving Linear Equations

  4. How much does it cost to mail a letter that weighs 3.2 ounces? The post office charges $0.20 for each additional ounce or fraction of an ounce; therefore, we must round the weight of the letter up to 4. Substitute 4 for the variable n and evaluate the expression. C = 0.45 + 0.20(n – 1) C = 0.45 + 0.20(4 – 1) C = 0.45 + 0.20(3) C = 0.45 + 0.60 C = 1.05 The cost of mailing a letter weighing 3.2 ounces is $1.05. 2.1.2: Solving Linear Equations

  5. How much does a letter weigh if it costs $1.85 to mail it? Using the same equation as in the previous question, substitute 1.85 in for C and solve for n. C = 0.45 + 0.20(n – 1) Original equation 1.85 = 0.45 + 0.20(n – 1) Substitute 1.85 for C. 1.40 = 0.20(n – 1) Subtract 0.45 from both expressions. 1.40 = 0.20n – 0.20 Distribute0.20 over (n – 1). 2.1.2: Solving Linear Equations

  6. 1.60 = 0.20n Add 0.20 to both expressions. 8 = n Divide both sides of the equation by 0.20. Since fractions of an ounce are charged at the same rate as full ounces, the weight of a letter that costs $1.85 to mail is greater than 7 ounces, but no more than 8 ounces. 2.1.2: Solving Linear Equations

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