[問題]考古題 Form22 sec7 DS-Q25

[凱薩琳]

Cars P and Q started simultaneously from opposite ends of a 300-mile expressway and traveled toward each other, without stopping, until they passed at location X. To the nearest mile , how many miles of the expressway had car P traveled when the two cars passed each other?

(1)Up to location X, the average speed of car Q was 15 miles per hour faster than that of car P

(2)Up to location X, the average speed of car Q was 1又1/3times that of car P

Ans:B

[Ace]

不管QP的速度或x距離
當PQ同時到達X時,所花的時間是一樣的
T=D/S

根據條件一
設P的速度為s,q為s+15
x到P的距離為x 到q為300-x
x/s=(300-x)/s+15
無法解方程式

條件二
設P的速度為s,q為1.3S
x到P的距離為x 到q為300-x
x/s=(300-x)/1.3s
1.3x=300-x
可求出x
故選B

[凱薩琳]

我想請問哪句有說"當PQ同時到達X時,所花的時間是一樣的"
謝謝...

[StanleyHuang]

第一句就是在講這件事喔~~~~
因為同時出發，所以相遇時兩台車所花的時間是一樣的~~