Question

在分区赛前，Unicorns 赢了他们篮球比赛的 $45 \%$ 。分区赛中，他们又赢六场、输两场，最终以胜率一半结束赛季。Unicorns 总共打了多少场比赛？

Before district play, the Unicorns had won $45 \%$ 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?

$48$

$50$

$52$

$54$

$60$

答案：A

知识点：一次方程百分数

难度评级：1550

解答：

设 Unicorns 分区赛前打了 $x$ 场比赛。那么分区赛前赢了 $0.45x$ 场，分区赛后共赢了 $0.45x+6$ 场。

他们总共打了 $x+8$ 场。题意给出 $0.45x+6=\dfrac{x+8}{2}.$

解得 $0.45x+6=0.5x+4$ ，所以 $2=0.05x$ ， $x=40$ 。因此 Unicorns 总共打了 $40+8=48$ 场。

所以正确答案是 A。

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

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

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

Thus, A is the correct answer.

2007 AMC 8 第 20 题

答案：A

难度评级：1550

解答：

其他年份的第 20 题