AMC8 2015

AMC8 2015 · Q3

AMC8 2015 · Q3. It mainly tests Rates (speed).

Jack and Jill are going swimming at a pool that is one mile from their house. They leave home simultaneously. Jill rides her bicycle to the pool at a constant speed of 10 miles per hour. Jack walks to the pool at a constant speed of 4 miles per hour. How many minutes before Jack does Jill arrive?

杰克和吉尔要去离家一英里的游泳池游泳。他们同时出发。吉尔骑自行车以10英里/时的恒定速度去游泳池。杰克以4英里/时的恒定速度步行去游泳池。吉尔比杰克早多少分钟到达？

(A) 5 5

(B) 6 6

(D) 9 9

(E) 10 10

Answer

Correct choice: (D)

正确答案：（D）

Solution

Jill takes $\frac{1}{10}$ of an hour, or 6 minutes, to get to the pool, and Jack takes $\frac{1}{4}$ of an hour, or 15 minutes, so Jill arrives $15 - 6=9$ minutes before Jack.

Jill 到游泳池需要 $\frac{1}{10}$ 小时，即 6 分钟；Jack 需要 $\frac{1}{4}$ 小时，即 15 分钟，因此 Jill 比 Jack 早到 $15 - 6=9$ 分钟。

Topics

AR.007 Rates (speed)