Question

Difficulty: MediumSolving Linear Equations

A shipping company charges a rate based on the weight of a package. The total cost CC, in dollars, to ship a package of weight ww pounds is given by the formula C=58(w2)+6.50C = \frac{5}{8}(w - 2) + 6.50 for packages weighing more than 22 pounds. If the shipping cost for a certain package is $14.00\$14.00, what is the weight of the package, in pounds?

Answer: 14 pounds

Answer

The weight of the package is 14 pounds.
Substituting C=14.00C = 14.00 into the formula gives 14.00=58(w2)+6.5014.00 = \frac{5}{8}(w - 2) + 6.50. Subtracting 6.506.50 from both sides yields 7.50=58(w2)7.50 = \frac{5}{8}(w - 2). Multiplying both sides by the reciprocal 85\frac{8}{5} yields 12=w212 = w - 2. Finally, adding 22 to both sides gives the weight w=14w = 14 pounds.

Step-by-Step Solution

1
Substitute the total shipping cost into the formula.
14.00=58(w2)+6.5014.00 = \frac{5}{8}(w - 2) + 6.50
Since the shipping cost CC is given as 14.0014.00, we substitute this value into the formula to solve for the unknown weight ww.
2
Subtract 6.506.50 from both sides of the equation.
7.50=58(w2)7.50 = \frac{5}{8}(w - 2)
Subtracting 6.506.50 isolates the term containing the variable ww on the right side of the equation.
3
Multiply both sides of the equation by the reciprocal of the fraction.
12=w212 = w - 2
Multiplying by 85\frac{8}{5} eliminates the fractional coefficient of 58\frac{5}{8} on the right side.
4
Add 22 to both sides of the equation to solve for ww.
w=14w = 14
Adding 22 isolates the variable ww, giving the final weight of the package.

Key Concept

Solving linear equations with fractional and decimal terms
Estimated Time:1m 30s
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