AMC10 2013 B

AMC10 2013 B · Q8

AMC10 2013 B · Q8. It mainly tests Rates (speed).

Ray’s car averages 40 miles per gallon of gasoline, and Tom’s car averages 10 miles per gallon of gasoline. Ray and Tom each drive the same number of miles. What is the cars’ combined rate of miles per gallon of gasoline?

Ray的小车平均每加仑汽油行驶40英里，Tom的小车平均每加仑汽油行驶10英里。Ray和Tom各行驶相同的里程。这些小车的综合平均每加仑汽油行驶里程是多少？

(A) 10 10

(B) 16 16

(D) 30 30

(E) 40 40

Answer

Correct choice: (B)

正确答案：（B）

Solution

Answer (B): Let $D$ equal the distance traveled by each car. Then Ray's car uses $\frac{D}{40}$ gallons of gasoline and Tom's car uses $\frac{D}{10}$ gallons of gasoline. The cars combined miles per gallon of gasoline is $\frac{2D}{\left(\frac{D}{40}+\frac{D}{10}\right)}=16.$

答案（B）：设 $D$ 为每辆车行驶的距离。那么 Ray 的车耗油 $\frac{D}{40}$ 加仑，Tom 的车耗油 $\frac{D}{10}$ 加仑。两车合计的每加仑行驶里程为 $\frac{2D}{\left(\frac{D}{40}+\frac{D}{10}\right)}=16.$

Topics

AR.007 Rates (speed)