Last Monday a certain store sold 17 wrenches at x dollars each

题目

Last Monday a certain store sold 17 wrenches at x dollars each. Last Tuesday the store reduced its prices and sold an additional 8 wrenches at 0.5x dollars each. Which of the following is equal to the average (arithmetic mean) price, in dollars, of the 25 wrenches that the store sold last Monday and Tuesday?

选项

0.68x

0.73x

0.76x

0.81x

0.84x

解析

设 x = 10 美元，则 0.5x = 5 美元。周一：售出17把扳手，每把10美元，总销售额为170美元。周二：售出8把扳手，每把5美元，总销售额为40美元。因此，这25把扳手的平均售价为 (170 + 40)/25 = 8.4 美元。现在将 x = 10 代入各选项验证，只有选项E的结果为8.4美元，因此答案为E。

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