Question

Randy 旅程的前三分之一在碎石路上行驶，接着在铺装路上行驶 $20$ 英里，剩下的五分之一在土路上行驶。Randy 的旅程总长多少英里？

Randy drove the first third of his trip on a gravel road, the next $20$ miles on pavement, and the remaining one-fifth on a dirt road. In miles, how long was Randy's trip?

$30$

$\dfrac{400}{11}$

$\dfrac{75}{2}$

$40$

$\dfrac{300}{7}$

答案：E

知识点：分数一次方程

难度评级：1150

解答：

铺装路占全程的比例为 $1 - \tfrac13 - \tfrac15 = \tfrac{7}{15}.$

因为这部分等于 $20$ 英里，所以全程为英里。 $20 \div \tfrac{7}{15} = \tfrac{300}{7}$

所以正确答案是 E。

The fraction of the trip on pavement is $1 - \tfrac13 - \tfrac15 = \tfrac{7}{15}.$

Since this equals $20$ miles, the whole trip is $20 \div \tfrac{7}{15} = \tfrac{300}{7}$ miles.

Thus, the correct answer is E.

2014 AMC 12B 第 3 题

答案：E

难度评级：1150

解答：

其他年份的第 3 题