Q21

[nanagyanewa]

Hello,

Can someone please explain to me why answer choice C is wrong for Q21? I solved this game the first time in late May and I solved it again today and got this answer wrong, yet again. I chose C over D (the correct answer) because R/T/S can all come before U so I don't understand why they chose R or T as flights that must be earlier than U and not S as well. Hope that makes sense. Any input is much appreciated.

[aileenann]

Thanks for reaching out! It's especially important to ask about a question like this, where you seem to have missed the answer more than once. This sounds like the sort of thing that might indicate a misunderstanding of what the question is asking or a misunderstanding of one or more of the constraints.

Let's take a look.

We now have the added condition of L-G for this particular problem, as well as knowing:

F-X-G
K = 2
L = U

Notice that now K must go before G (because G has F plus one other element go before it), F must go before G, and L must go before G. Thus of all the pilots, G *must* go last. There is simply no other pilot slot that G can fill because all three other pilots have to go first. Also since K must go 2nd, that means that the only uncertainty as to the pilots is whether F or L goes first (with the other going 3rd).

The question is asking us which of the following could be false. That means that 4 of the answers cannot be false/must be true and one can be false (this doesn't mean it necessarily has to be false, just that it can be false if we want it to be false).

Let's look at (C). This says that either R or T's flight is earlier than U's flight. We kow that U goes with L, so this also the same as saying that either R or T goes before L. Can this be false?

If it's false that means that U has to go before both R and T. This in turn means that L has to go in the first slot, pushing F to the 3rd slot. However, if L goes in the first slot, there won't be an element in between F and G as is required by one of the initial constraints. Hence (C) cannot be false, and so is not the answer.

I hope this helps Let me know if you have follow-up questions or concerns.

[nanagyanewa]

Thanks a bunch for the response. I guess I was confused about the "either or" statement but your explanation helped make it clear.

[aileenann]

Awesome. It is always nice to know when confusion gets cleared up!