Question

Randy 旅程的前三分之一是在碎石路上行驶，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：900

解答：

设全程为 $t$ 英里，则 $\begin{aligned}t &= \dfrac t5 + 20 + \dfrac t3 \\ t &= 20 + \dfrac {8t}{15} \\ \dfrac 7{15} t &= 20\\ t &= \dfrac{300}7.\end{aligned}$

所以正确答案是 E。

Let the path distance be $t.$ Then, we get: $\begin{aligned}t &= \dfrac t5 + 20 + \dfrac t3 \\ t &= 20 + \dfrac {8t}{15} \\ \dfrac 7{15} t &= 20\\ t &= \dfrac{300}7.\end{aligned}$

Thus, the correct answer is E .

2014 AMC 10B 第 3 题

答案：E

难度评级：900

解答：

其他年份的第 3 题