Question

从 Dallas 到 Houston 的巴士每小时整点发车。从 Houston 到 Dallas 的巴士每小时半点发车。两城之间的行程需要 $5$ 小时。假设巴士都在同一条公路上行驶，一辆开往 Houston 的巴士会在公路上（不在车站内）遇到多少辆开往 Dallas 的巴士？

Buses from Dallas to Houston leave every hour on the hour. Buses from Houston to Dallas leave every hour on the half hour. The trip from one city to the other takes $5$ hours. Assuming the buses travel on the same highway, how many Dallas-bound buses does a Houston-bound bus pass on the highway (not in the station)?

$5$

$6$

$9$

$10$

$11$

答案：D

知识点：路程、速度与时间

难度评级：1260

解答：

考虑一辆 $6\!:\!00$ 从 Dallas 出发、 $11\!:\!00$ 到 Houston 的巴士。它会遇到所有在这段时间内与它同在公路上的开往 Dallas 的巴士。

开往 Dallas 的巴士每半点从 Houston 出发，行程 $5$ 小时。与这辆车在路上相遇且不在车站相遇的，是 $1\!:\!30, 2\!:\!30, \ldots, 10\!:\!30$ 从 Houston 出发的巴士，共 $10$ 辆。

所以正确答案是 D。

Consider a bus leaving Dallas at $6\!:\!00,$ arriving in Houston at $11\!:\!00.$ It meets every Dallas-bound bus that is on the highway during that window.

Dallas-bound buses leave Houston on the half hour and take $5$ hours. The ones sharing the road (meeting away from a station) are those that left Houston at $1\!:\!30, 2\!:\!30, \ldots, 10\!:\!30,$ which is $10$ buses.

Thus, the correct answer is D .

1995 AMC 8 第 25 题

答案：D

难度评级：1260

解答：

其他年份的第 25 题