Could use help on this one

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Ilikemeat321: Junior | Next Rank: 30 Posts; Posts: 26; Joined: Thu Jul 24, 2008 7:33 am

Could use help on this one

by Ilikemeat321 » Tue Aug 19, 2008 10:22 am

Car X leaves Town A at 2 p.m. and drives toward Town B at a constant rate of m miles per hour. Fifteen minutes later, Car Y begins driving from Town B to Town A at a constant rate of n miles an hour. If both Car X and Car Y drives along the same route, will Car X be closer to Town A or Town B when it passes Car Y?

1. Car X arrives in town B 90 minutes after leaving city A
2. Car Y arrives in Town A at the same time Car X arrived in Town B

I got C...can someone explain how to get the right answer

Quote

Source: Beat The GMAT — Data Sufficiency | Tue Aug 19, 2008 10:22 am

pepeprepa: Legendary Member; Posts: 661; Joined: Tue Jul 08, 2008 12:58 pm; Location: France; Thanked: 48 times

by pepeprepa » Tue Aug 19, 2008 11:45 am

That's a nice one question, thanks for posting it.

1)
We are ok it is useless by itself.

2) Car Y arrives in Town A at the same time Car X arrived in Town B
We have two cars. We have two different speeds. We know X starts 15' before Y, and they arrive at their destination at the same time and drove the same number of kilometers; we can infer that the speed of X is lower than the speed of Y.

You have the city A, the city B and the middle of the distance is M.
A-------------M----------------B

Imagine X see Y between A and M, there is a big problem because X is slower than Y and X has to drive more kilometers than Y ! X will never arrive at B at the same time Y does at A.
That is the same if they see each other at M, it's over for X, it is slower than Y.
So, X will see Y between M and B, closer to B than to A.

So your answer is B