Is the answer wrong? -- Data sufficiency in simple maths

julia27 · 发表于 2015-5-12 20:44:44

Here is the problem:
Two racecar drivers, A and B, are driving around a circular track. If A is 200 meters behind B and both drivers drive their respective constant rates, how long, in second, will it take for A to catch up to B?

The circumference of the racetrack is 1,400 meters.
B is driving 25 meters per minute faster than A.

Given answer is (B)

My questions:
1. B is faster than A, how can A catch up to B? Shouldn't it be B to catch up to A?
2. Then, if B is catching up A on a circular track, the difference between them is not 200 meters, but (the circumference - 200) meters, right? Thus my asnwer is actually (C)!
Don't laugh...

julia27 · 发表于 2015-5-13 23:52:36

no reply

ihaveausdream · 发表于 2015-5-14 01:28:44

这个题我同意你

因为B比A快，所以实际上是B超圈赶上了A，这时再相遇时，B走的－A走的＝1400-200

画个图就看出来了。。。

julia27 · 发表于 2015-5-16 22:59:47

ihaveausdream 发表于 2015-5-14 01:28
这个题我同意你

因为B比A快，所以实际上是B超圈赶上了A，这时再相遇时，B走的－A走的＝1400-200

谢谢你

Is the answer wrong? -- Data sufficiency in simple maths

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