Question

一名大学生周末开小型车回家 $120$ 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：调和平均数速率

难度评级：980

解答：

回家用了 $120/30=4$ 加仑，返程用了 $120/20=6$ 加仑，共用 $10$ 加仑，行驶 $240$ 英里。

平均为 $240/10 = 24$ 英里/加仑。

所以正确答案是 B。

The student used $120/30=4$ gallons driving home and $120/20=6$ gallons returning, for $10$ gallons over $240$ miles.

The average is $240/10 = 24$ miles per gallon.

Thus, the correct answer is B.

2007 AMC 10B 第 3 题

答案：B

难度评级：980

解答：

其他年份的第 3 题