Question

一名大学生开小型车回家过周末，路程 $120$ 英里，平均每加仑行驶 $30$ 英里。返程时他开父母的 SUV，平均每加仑只能行驶 $20$ 英里。往返全程平均每加仑行驶多少英里？

A college student drove his compact car $120$ miles home for the weekend and averaged $30$ miles per gallon. On the return trip the student drove his parents' SUV and averaged only $20$ miles per gallon. What was the average gas mileage, in miles per gallon, for the round trip?

$22$

$24$

$25$

$26$

$28$

答案：B

知识点：路程、速度与时间调和平均数

难度评级：990

解答：

去程用 $120/30=4$ 加仑，返程用 $120/20=6$ 加仑。

往返共 $240$ 英里，用油 $10$ 加仑，所以平均每加仑行驶英里。 $\dfrac{240}{10}=24.$

所以正确答案是 B。

The trip home uses $120/30=4$ gallons, and the return trip uses $120/20=6$ gallons.

The round trip covers $240$ miles on $10$ gallons, so the average is $\dfrac{240}{10}=24.$

Thus, the correct answer is B.

2007 AMC 12B 第 2 题

答案：B

难度评级：990

解答：

其他年份的第 2 题