AMC12 2007 B

AMC12 2007 B · Q2

AMC12 2007 B · Q2. It mainly tests Rates (speed), Arithmetic misc.

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?

一名大学生开他的紧凑型汽车行驶 $120$ 英里回家过周末，平均油耗为每加仑 $30$ 英里。返程时该学生开父母的 SUV，平均油耗只有每加仑 $20$ 英里。往返行程的平均油耗（英里/加仑）是多少？

(A) 22 22

(B) 24 24

(D) 26 26

(E) 28 28

Answer

Correct choice: (B)

正确答案：（B）

Solution

The trip was $240$ miles long and took $\dfrac{120}{30}+\dfrac{120}{20}=4+6=10$ gallons. Therefore, the average mileage was $\dfrac{240}{10}= \boxed{\textbf{(B) }24}$

往返路程共 $240$ 英里，耗油量为 $\dfrac{120}{30}+\dfrac{120}{20}=4+6=10$ 加仑。因此平均油耗为 $\dfrac{240}{10}= \boxed{\textbf{(B) }24}$

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