GMAT Question of the Day - Problem Solving - Overlapping Sets/Picking Numbers
At a certain rail-yard each train is either a freight train or a commuter train and either runs on the southern line or the northern line. 20% of the commuter trains run on the southern line and the number of freight trains that run on the southern line represents 20% of the total trains at the rail yard. If the commuter trains represent 44% of the total trains at the rail yard, approximately what percent of the trains run on the northern line?
GMAT Question of the Day Solution
These GMAT overlapping sets questions are straightforward but take some organizing so it's important to take your time with the set-up. On the whole, the GMAT is an organizational challenge. Try picking a value for the total. That should make things easier. Whenever you are dealing with a question that has variables or percents/proportions in the answer choices consider picking numbers to make the question more concrete. Also, did you define what you were looking for: Northern/Total? Defining the question will help you plan your work and will draw you towards the solution.