Q8

[walkerdoreen07]

Hello! This is my first posting!

I don't understand pt 42 s1 g2 Q8, I get confused when the question has "completely determined" in it. Im thinking that I have to determined how many slots can M_G go in for Q8. Don't know how to begin...

Thank you!

[aileenann]

Hello and welcome to the Atlas forums! We're so glad you've started posting.

Before getting into the meat of this question, let's first think about what it means to be "completely determined." If something is completely determined, that means there is no uncertainty left with respect to whatever that is. For example, if the position of M is completely determined, that means I know it definitely goes in slot # 4, for example (or wherever). If you cannot definitively say where something will *definitely* be in a given setup, then it is not completely determined. Completely determined in this scenario means you can put a precise number on it.

Now, getting into the meat of this problem, let's first make sure we're on the same page in terms of setup. Generally, students reach the following setup:

T---L---G
F---P
P/T


Notice that I use "P/T" to denote that they go next to one another but that I don't know in which order. This "P/T" is the part of the setup I find that most often confuses students. However if you think about it, once we know that P and T go right next to one another, we also know that F must come before T as well because how else could it go before P if T and P are directly next to one another. This means (hard to see at first glance) that we can actually join up these two separate subtrees, ultimately reaching:

F---P/T----L----G

With M being a "floater" in the sense of being able to go anywhere, so far as I can tell.

Now that we know this, this game looks pretty straightforward actually. We know the exact order that many of the elements have to go in. The only elements of uncertainty left in this game is where M fits into the following order and the order of the P/T pair. Hence, when we are figuring out exactly how many elements have a completely determined question in a particular game, we are going to think most especially about these two remaining elements of uncertainty.

Now to the question. They tell us as an additional constraint for this game that there is exactly one space between M and G. If we add this information to our diagram above, we see that the only element that could go singly between M and G is L. Therefore we are really looking now at:

F---P/T---MLG.

What's more, we only have six slots, so we are really looking at:

F(P/T)MLG

That is we know exactly where F, M, L, and G have to go (which slot number). The only thing we still don't know is whether P or T goes first within their pair. Hence, in this question we know with certainty 4 out of 6 of the elements' positions.

I hope this helps. Please feel free to follow up with a reply if anything needs further clarification or if you have any other insights to add to the problem

[walkerdoreen07]

Thank you for quick response!!! The definiation of "completely determined" was very clear. I had the right setup, but i forgot about the "L".

[ptraye]

the question says, "If there is exactly one bay between the bay holding machinery and the bay holding grain, then..."

i got this question correct the first time i tried this problem, and wrong this time, a week later....

when i read the question this time, i thought there are two options:
M_G or G_M.

with these two options, the way the question is written, i thought the layout could be:
F T/P M L G or
F T/P G L M

the question only says there is one bay between, but it does not mention the order of M & G, so I chose answer (A) this time saying that there is only 2 known positions for the bays.

What do you think?

[timmydoeslsat]

L always has to be before G in our global rules. So the second hypothetical would not work here.