Which one of the following could be the order, from first to last, in which the five planes depart?

Maybeillgetlucky on May 3, 2019


I've watched the game setup. I'm still perplexed as to how you came up with those 3 scenarios. how did you know to do that on this question? it's so challenging without doing that but I wouldn't know how/when to make a set up like that. how do you know with 100% certainty to commit time to creating those scenarios in the beginning rather than just moving to the questions?

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shunhe on January 12, 2020

Hi @Maybeillgetlucky,

Thanks for the question! I wouldn't call it "knowing with 100% certainty" to do the diagrams. It's more of an art than a science, and under the pressure of a timed exam, most students won't be able to come up with these sorts of diagrams. However, generally speaking, it's as good to take your deductions as far as possible when making your set-up, which will help you more quickly reach correct answer choices as you work your way through the questions. Something that could tip you off to making the three scenarios here is noting that there are ONLY three scenarios, as the instructor described. We know whether 3/5 flights are international or domestic, but we don't know between the other two. Either they're both domestic, both international, or one's domestic and one's international (and they are interchangeable, since no other rule applies to them). We also can note that a lot of the problem hinges on whether the flights are domestic or international. The order of the flights is in part determined by whether or not a flight is domestic or international. Since so much hinges on the potential international/domestic status of S and T, at the beginning, we can note that it might be worthwhile to sketch out these three possibilities. The question isn't terribly complicated, so it's not sketching out 3 messy scenarios that we wouldn't be able to keep track of. And it's only 3 scenarios - if there were 5 or 6, for example, we might not want to diagram out each scenario, as doing so would take a good amount of time. Based on all these factors, we can conclude that it might be worth it to diagram out the scenarios, and in this case, it is. Hope this helps! Feel free to ask any other questions if you have them.

Gabby_teixeira on April 6, 2020

Hi! What's the quick thought process for knowing in which ways are arrows should point in sequences?