gmat1393 wrote:
The Middlebury train station is between the Appleton and Lancaster stations and all three are serviced by the same track. What is the distance between Middlebury and Lancaster?
(1) If a train can travel 50 miles on one pound of coal, it will use twice as much coal traveling from MiddleBury to Lancaster as it will use to travel between Middlebury and Appleton.
(2) Traveling from Appleton to Middlebury at an average rate of 35 mph takes 30 minutes longer than at an average rate of 55 mph.
Questions involving distance will likely be based either on the speed*time=distance equation or some kind of ratio/subtraction between the whole (Appleton-Lancaster) and its parts (Appleton-Middlebury, Middlebury-Lancaster).
We'll look for these pieces of information, a Logical approach.
(1) This gives us the ratios between the distances, not exact numbers.
Insufficient.
(2) This lets us calculate the Appleton-Middlebury distance (as we can create an equation with 1 variable) which is insufficient on its own.
Insufficient.
Combined:
(2) gives us the Appleton-Middlebury distance and (1) gives us the ratio between the Appleton-Middlebury to Middlebury- Lancaster distances.
Sufficient!
(C) is our answer.
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63% (02:20) correct 
