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Calculate the number of songs downloaded based on the cost of joining and downloading songs in an internet music club.
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EXAMPLE 1 Solving a Real-World Problem Music Club You pay $9.95 to join an Internet music club. You pay $.99 for each song that you download. Your cost for joining and downloading some songs is $17.87. How many songs did you download?
The model below represents a way of finding how many songs you downloaded. You can use xto represent the number of songs. EXAMPLE 1 Solving a Real-World Problem
9.95 + 0.99x = 17.87 –9.95 –9.95 0.99x 7.92 = 7.92 0.99x 0.99 0.99 ANSWER You downloaded 8 songs. EXAMPLE 1 Solving a Real-World Problem SOLUTION Write an algebraic model. Subtract9.95from each side to undo addition. Simplify. Divide each side by 0.99 to undo multiplication. x = 8 Simplify. xis by itself.
? 9.95 8 = 17.87 + 0.99 ? 9.95 + 7.92 = 17.87 17.87 = 17.87 GUIDED PRACTICE for Example 1 1.Show how to check the solution in Example1.
Cost to join + Cost per song Number of songs = Total cost 9.95 + 0.99x = 26.78 –9.95 –9.95 0.99x 16.83 = GUIDED PRACTICE for Example 1 2. What If? Suppose the cost to join and download some songs is $26.78. How does this change the equation in Example 1? Find the number of songs. SOLUTION Write an algebraic model. Subtract9.95from each side to undo addition. Simplify.
16.83 0.99x = 0.99 0.99 x =17 ANSWER You downloaded 17 songs. GUIDED PRACTICE for Example 1 Divide each side by 0.99 to undo multiplication.
ANSWER You developed 19 rolls of films. GUIDED PRACTICE for Example 1 3. Film You pay $35 in dues to a photo club and $10 per roll you have developed. If you spend $225 during the year, how many rolls of film do you have developed? Use 10x+ 35 = 225 and solve for x.