Question

琼斯第一次旅行走了 $50$ 英里。后来一次旅行中，他以原来三倍的速度走了 $300$ 英里。新旅行时间与原旅行时间相比是：

Jones covered a distance of $50$ miles on his first trip. On a later trip he traveled $300$ miles while going three times as fast. His new time compared with the old time was:

三倍

three times as much

两倍

twice as much

相同

the same

一半

half as much

三分之一

a third as much

答案：B

知识点：rate-time-distance proportional reasoning

难度评级：1150

小提示：

将每次旅行时间写成路程除以速度

Write each travel time as distance divided by speed

大提示：

若原速度为 $v$ ，比较 $\frac{50}{v}$ 与 $\frac{300}{3v}$

If the old speed is $v,$ compare $\frac{50}{v}$ with $\frac{300}{3v}$

解答：

若第一次的速度为 $v$ ，则原旅行时间为 $\frac{50}{v}$ 。后一次的旅行时间为 $\frac{300}{3v}=\frac{100}{v}=2\left(\frac{50}{v}\right)\text{。}$ 因此，新旅行时间是原来的两倍。

正确答案是 B。

If the first speed was $v,$ the old time was $\frac{50}{v}.$ The later time was $\frac{300}{3v}=\frac{100}{v}=2\left(\frac{50}{v}\right).$ Thus the new time was twice the old time.

The correct answer is B.

1956 AMC 12 第 22 题

答案：B

难度评级：1150

小提示：

大提示：

解答：

其他年份的第 22 题