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Current time:0:00Total duration:5:53

- [Instructor] Let's take a look at an ordering setup together. We'll start by examining
the introductory passage and that will help us understand what we're being asked to do. So we're told that exactly five objects, J, K, L, M, and N are to be stacked one on top of the other. Their resulting positions are numbered from one through five, from bottom to top. The resulting stack must meet
the following restrictions. All right, so the first
thing we can notice is that the primary
players are five objects. We'll make a list of them here, so that we can keep track of them. We've got J, K, L, M, and N. Now, what are we doing with these objects? Well, they're stacked vertically and we're basically meant
to determine what order they're stacked in. We're not seeing any kind of
grouping action happening, so that means this is a
classic ordering setup. Let's make a diagram that
looks like our situation. Five objects stacked one on top of another and that can look like five
spots in the vertical column. And, we're told that
the bottom is number one and the top is number five. Gosh, can you imagine
getting this part backwards on test day? It would be a nightmare, so it's a good idea to never
rush just for the sake of time, because it is so much more
costly to have to go back and fix mistakes, than it is to just take your
time with important details. At this point, we have a basic diagram and we can move on to the rules. Our first rule is that L is immediately above K in the stack. There's always various ways to notate different kinds of rules. We like putting a pair
in a box, like this. Our second rule is that
J is not in position one. Whenever we can mark a rule
directly in our diagram, it's a good idea to do so, instead of noting it off to the side. This way, it's clearer,
we see it all the time. We can show that J isn't in position one by writing J with a line through it. The third rule tells us
that M is not immediately below K in the stack. We can illustrate this in a similar way as we did in Rule One, except this time we can
put a line through it to show that this
situation doesn't happen. So, M below K, but with a line through it to show that it can't
ever happen this way. Finally, the fourth rule tells us that N is either in position one, or else in position five. Just like with Rule Two, we can mark this directly
into our diagram. You can use arrows like this or whatever makes the most sense to you and is clear and consistent. Okay, we've notated all the rules either directly into the
diagram or off to the side so that we don't forget them. We've set ourselves up for
one of the most important aspects of analytical reasoning now, which is making deductions. So what definites can we deduce that weren't explicitly told to us? Well, Rule One is that L
is immediately above K. If we think about combinations for where these two could go, there's just too many of 'em, so we don't want to sit
there on test day and think, where are all the places L and K could go? What we know for sure is,
where L and K can't go. So, if L is always immediately
above K in the stack, then L can't be first and K can't be fifth. We weren't explicitly
given that information, but we know that it must be true, because if L is immediately above K, then L can't be on the bottom and K can't be on the top. Since we know that it's true, that is what a deduction is, something that we weren't
told, but we can infer. J can be in four different
spots so that doesn't help us. The only thing we know about K and L is that there's one place
each that they can't be. We know next to nothing about M, only that it can't be below K and we don't know where K is, and N is so far the
most restricted object, because there are only
two places N can go. So, having checked for more deductions and not finding any, we
can move to the questions. To recap, we just set up an ordering task, using dashes for the spots. We noted some rules off to the side and some directly in the diagram and we made one deduction
based on Rule One. Even though we don't know
where any of the objects go for sure, we're in a really good position
to move to the questions, because we have an initial diagram that we'll use for support, as well as a solid
understanding of the rules. It's likely that some of
the questions will give us extra information to use that will allow us to make more deductions for those questions, so don't get worried on test day, if you finish a setup and you don't have any
of the spots determined. That will happen sometimes. Have confidence that you've
made the deductions that you can and now you can move to the questions.