Ordering setup | Given info–must be true | Worked example

- [Instructor] Before you dive into the questions for this setup, make sure to watch the setup video, in which we created our initial diagram using the rules, and in which we made deductions from those rules. We're asked which one of the following must be true. So this question is asking us for what has to be true, given information in the setup. And that means that the answer will always be true, in every situation. Usually, we could use our initial diagram to identify the answer pretty quickly. But sometimes, just as in this question, it isn't immediately apparent, and we're gonna have to do some work. None of the choices here are reflected in either our diagram or in our big chain of elements. For example, A says that F is later than M, but that isn't directly represented in our chain, since M and F aren't connected. B says that F is later than S, but we don't even know anything about S. So it's very likely that this choice is wrong. S just isn't restricted in any way. C says that H is later than F, but we don't see that in our group here because H and F aren't directly connected. Let's leave this open. Choice D is suspect for the same reason that B is because it's most likely not true that S has to relate to any other monument in some kind of way since there are no rules about S. So we can pretty safely cross this one out. And E is that M is later than G. Again, look at our chain. We don't know this to be true so far because M and G aren't directly related. On test day, if you're short on time at this point, you could tentatively pick either A, C, or E, and then circle the whole question to come back to later, knowing that you've at least eliminated two choices strategically, and given yourself a better mathematical chance. And then if you had time later, you could come back and test the three choices, which we're going to do right now. A, does F have to be later than M? Well, let's look at what we know about each of these monuments. We know that M is either one, two, or three. We also know that F is either three, four, or five. Now, they do overlap by being able to be in 603, but remember that there's no way that they could both be on the same day in 603. So F is going to be later than M no matter what. And we shouldn't feel bad that we didn't see this deduction initially. It's a fairly tough one to see. But we worked it out just fine nonetheless. I'll go through all the wrong choices, even the ones that we crossed out, just in case you have questions on them. B, F was begun in a later year than S. This could be false because F could be earlier than S. For example, if we had G, M in one, then L, then F, then, S, and then H. C, H was begun in a later year than F. This could be false. H could be earlier than F. For example, if we did G, M first again, L second, S third, H fourth, and F fifth. D, H was begun in a later year than S. This could be false. H could be earlier than S. For example, if we had G, M in one, L in two, F in three, H in four, and S in five. And finally, choice E says that M was begun in a later year than G. But this doesn't have to be true because M could be earlier than G. We could put M, S in one, G in two, L in three, F in four, and H in five. So the answer is A.