Question

Roy 买了一辆新的电池汽油混合动力汽车。一次旅行中，汽车前 $40$ 英里只使用电池，之后的路程只使用汽油，每英里耗油 $0.02$ 加仑。整趟旅行平均每加仑行驶 $55$ 英里。这趟旅行总长多少英里？

Roy bought a new battery-gasoline hybrid car. On a trip the car ran exclusively on its battery for the first $40$ miles, then ran exclusively on gasoline for the rest of the trip, using gasoline at a rate of $0.02$ gallons per mile. On the whole trip he averaged $55$ miles per gallon. How long was the trip in miles?

$140$

$240$

$440$

$640$

$840$

答案：C

知识点：速率一次方程

难度评级：1370

解答：

设汽车只用汽油行驶的距离为 $x$ ，则交叉相乘并化简得因此旅程总长为 $400 + 40 = 440$ 。 $\dfrac{40 + x}{0.02x} = 55.$ $40 = .1x$ $x = 400.$

所以正确答案是 C。

Let $x$ be the distance the car drove solely on gasoline. We have that $\dfrac{40 + x}{0.02x} = 55.$ Cross-multiplying and simplifying gives $40 = .1x$ $x = 400.$ The total length of the trip is then $400 + 40 = 440.$

Thus, C is the correct answer.

2011 AMC 10A 第 15 题

答案：C

难度评级：1370

解答：

其他年份的第 15 题