Station Q is to the East of Station T. At 12 noon, a train starts from

Question

Station Q is to the East of Station T. At 12 noon, a train starts from Station Q and travels at a constant speed of x mph towards Station T. At 12 noon of the same day, another train starts from Station T and travels at a constant speed of y mph towards Station Q. At what time will the trains meet?

(1) y = 4x/3
(2) x = 100 mph

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arushi118 · Answer

We cannot find time when the trains will meet as the distance between the 2 stations is unknown.
Using relative speed: Time required to meet = d/(x+y) where d is the distance between the 2 stations. So, we cannot find the time using the information given.
Answer is E.

paragw · Answer

This is a typical train meeting problem where meeting time formula with distance is:

t = Distance between stations / Sum of speeds
Without the distance, times are relative expressions only.
Hence,  E

Dereno · Answer

Station Q is to the left of Station T. And two trains start exactly at 12 noon, from both stations Q and T.

The speeds of the train from stations Q and T are x mph and y mph respectively.

We need to find the time of meet = T = ?

Speed = Distance / Time

T = Distance / Relative speed

Statement 1:

(1) y = 4x/3

T = Distance / ( x + 4x/3)

Since, we don’t know the values of Distance, or the variable x. Hence,  Insufficient.

Statement 2:

(2) x = 100 mph

we don’t know the values of y and distance. Hence,  Insufficient.

Combining statements 1 and 2, we get

x = 100 mph.

y = 4x/3 = 400/3 mph.

Time = distance / (100 + 400/3)

Since distance is not given. Hence,  Insufficient

Option E

Ayeka · Answer

Let the distance between the two stations = D
They meet when time = distance/combined speed = D/(x + y)

(1) y=4x/3 
Meeting time= D/(x+4x/3) = 3D/7x 
D and x are unknown 
Hence, insufficient

(2) x=100mph 
Meeting time= D/(100+y) 
D and y are unknown. 
Hence, insufficient

Combining both 
Meeting time= D/(100+400/3) =3D/700 
We can’t find the meeting time of train without distance. Hence, insufficient.

Answer: E

Souradeep17 · Answer

We need to find the meeting point but for that we need to know the distance between them.

Option 1:
Time to meet will be Distance /(sum of speed)
D/(x+4x/3)

Not sufficient
Option 2:
X=100 no info about y, nor we know distance hence not sufficient

Option 1+2:
from both the options also we don't know about the distance between T & Q hence option E should be the answer

Reon · Answer

Station Q is to the East of Station T. At 12 noon, a train starts from Station Q and travels at a constant speed of x mph towards Station T. At 12 noon of the same day, another train starts from Station T and travels at a constant speed of y mph towards Station Q. At what time will the trains meet?

(1) y = 4x/3
(2) x = 100 mph

Here, the distance between the two station is unknown. So it is not possible to find the meeting time of two trains without knowing the distance. 
Time of meet = Distance/Sum of Speeds of Train 
In both (1)&(2) either speed is given or relation between them. But there is no info about distance. Hence, insufficient to find the meeting time of trains.

E

Station Q is to the East of Station T. At 12 noon, a train starts from

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GMAT Data Sufficiency (DS) Questions

Station Q is to the East of Station T. At 12 noon, a train starts from

Prep Toolkit

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My Rewards