2007 AMC 8 Problem 20

Below is the professionally curated solution for Problem 20 of the 2007 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2007 AMC 8 solutions, or check the answer key.

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Concepts:linear equationpercentage

Difficulty rating: 1550

20.

Before district play, the Unicorns had won 45%45 \% of their basketball games. During district play, they won six more games and lost two, to finish the season having won half their games. How many games did the Unicorns play in all?

4848

5050

5252

5454

6060

Solution:

Let xx be the number of games the Unicorns had played before district play. Then they had won 0.45x0.45x games before district play and 0.45x+60.45x+6 games after district play.

In total, they played x+8x+8 games. The problem statement tells us that 0.45x+6=x+82.0.45x+6=\dfrac{x+8}{2}.

Solving gives 0.45x+6=0.5x+40.45x+6=0.5x+4, so 2=0.05x2=0.05x, and x=40x=40. Therefore, the Unicorns played 40+8=4840+8=48 games in all.

Thus, A is the correct answer.

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