speed and distance

[vaibhav101]

train Xleaves LA at 10 am and travels east at a constant speed of x m/h. if another train Y leaves LA at 11:30 am and travels east along the same tracks at speed y m/h , then at what time will train Y catch train X?

1) y=4x/3
2) X=60 m/h

[Jay@ManhattanReview]

Train X leaves LA at 10 am and travels east at a constant speed of x miles per hour. If another train Y leaves LA at 11:30 am and travels east along the same tracks at speed y miles per hour, at what time will train Y catch train X?

1) y = 4x/3
2) X = 60 miles per hour

Given:
1. Train X leaves LA at 10 am and travels east at a constant speed of x mph
2. Train Y leaves LA at 11:30 am and travels east at a constant speed of y mph

Question: At what time will train Y catch train X?

Train Y can catch train X if its speed y is greater than the speed of train X, x. Since the trains are meant to run infinitely, train Y will definitely catch train X. So, to get the time when Y catches X, we must either know the values of x and y, or relation between x and y. Statement 1 provides the same. Sufficient. Statement 2 is certainly insufficient as it does not provide the value of y.

The correct answer: A

Hope this helps!

-Jay
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