Linear Setup Practice Drill #11

[Shar14]

Greetings,

I am in the process of training myself on how to identify Not Laws. On page 122, for question 11 the diagram says that Z cannot go in spaces 1,6,7 or 8. I am having a very hard time understanding why Z cannot go in space 6 as one of the conditions says that only one space is between Z and T. With that being said, I would have thought Z can go in space 6 so that T can go in space 8.

I don’t know if the answer is obvious but I have used enough brain power trying to understand... please help lol

[Dave Killoran]

Hi Shar,

Thanks for the question! I've moved your post into the appropriate section, which is for the LG Bible, and specifically into our Chapter 3 forum.

Here's a general tip for dealing with Not Laws that you can't see at first: try placing the variable in question into that slot, and see what happens as a result. When a variable can't be in a particular space, when you try to put it there you will find that you can't create a workable solution to the problem. That's a great way to reverse engineer the issue, and find the root of what causes the Not Law.

So, let's apply that here: what if Z is picked up 6th? the following happens:

• When Z is 6th, T would be 8th. So far, so good.
  Now let's look at other rules involving Z and T since both are locked in place.
  With Z picked up 6th, from the second rule Y must be picked up 3rd.
  With T picked up 8th, from the first rule V must be picked up 5th.
  Again, so far, so good. Now let's look at what happens as a consequence of Y and V being placed.
  With Y picked up 3rd, from the fourth rule S must be picked up 8th. Uh oh, we have a problem since T is already there.
  
  Thus, the chain that must follow when Z is placed 6th results in a scenario that cannot meet the rules. Thus, Z can never be 6th (nor can T be 8th)

The approach above shows what happens when you start placing variables, and the domino effect that follows thereafter. But, could we have seen that faster, or at least been suspicions there was an issue? YES! We can find this connection from linking Z through the second rule, and then the Z __ T split-block created by the third and fifth rules. Any time Z is NOT 3rd, then Y will be 3rd and S will be 8th. That will affect the placement of the Z __ T block, hence the Not Laws above.

Please let me know if that helps. Thanks!

[leslie7]

very helpful i had the same question - ty for the clear answer !