AMC10 2007 B

AMC10 2007 B · Q3

AMC10 2007 B · Q3. 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?

一位大学生开车 120 英里回家过周末，平均油耗 30 英里/加仑。回程时他开父母的 SUV，平均油耗只有 20 英里/加仑。往返总油耗平均是多少英里/加仑？

(A) 22 22

(B) 24 24

(D) 26 26

(E) 28 28

Answer

Correct choice: (B)

正确答案：（B）

Solution

Answer (B): The student used $120/30 = 4$ gallons on the trip home and $120/20 = 6$ gallons on the trip back to school. So the average gas mileage for the round trip was $$\frac{240\ \text{miles}}{10\ \text{gallons}} = 24\ \text{miles per gallon}.$$

答案（B）：学生回家路上用了 $120/30 = 4$ 加仑汽油，返校路上用了 $120/20 = 6$ 加仑汽油。因此往返行程的平均油耗里程为 $$\frac{240\ \text{miles}}{10\ \text{gallons}} = 24\ \text{miles per gallon}.$$ （即每加仑 24 英里。）

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