On a sheet of paper, make a list of all the geometric formulas that are used in this section. Step 3: Translate the information that appears in English into an algebraic equation. We will use a known geometry formula. How do we know which formula to use? List the information we are given and what we want to fi nd: The court is in the shape of a rectangle; its area 2808 ft2 and its length 78 ft. We must fi nd the width. Which formula involves the area, length, and width of a rectangle? A lw Substitute the known values into the formula for the area of a rectangle, and solve for w. A lw 2808 78w Substitute the known values. Step 4: Solve the equation. 2808 78w 2808 78 78w 78 Divide by 78. 36 w Simplify. Step 5: Check the answer and interpret the solution as it relates to the problem. If w 36 ft, then lw (78 ft)(36 ft) 2808 ft2. Therefore, the width of the tennis court is 36 ft. Remember to include the correct units in your answer! YOU TRY 3 Write an equation and solve. The area of a rectangular room is 232 ft2. Find the length of the room if the width is 14 1 2 ft. Sometimes, a problem will contain two unknown values. Michelle built a new rectangular stall for her horse. She used 52 ft of fencing, and the length of the stall is 2 ft more than the width. Find the dimensions of the stall. Solution Step 1: Read the problem carefully, and identify what we are being asked to fi nd. We must fi nd the length and width of the stall. A picture will be very helpful. Step 2: Choose a variable to represent an unknown, and defi ne the other unknown in terms of this variable. The length is 2 ft longer than the width. Therefore, let w the width of the stall EXAMPLE 4 www.mhhe.com/messersmith SECTION 4.5 Solving Geometry Applications Using Algebra 335
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