# If the fifth floor is examined on Friday, which one of the following must be true?

Marissa on May 19 at 11:42PM

Why E?

I found both D and E to work. Can someone please work this question out so I can see why D is incorrect? Thank you!

on May 25 at 12:32AM

Hello @Marissa-Avnaim,

When I see that the 5th floor is on Friday, the first thing that comes to my mind is the 4th floor. Because consecutive numbers can't share a day, I know that it must be on Thursday.

_ _ _ _

_ 4 5 _
W T F S

Based on my 3 - 7 - 5 arrangement, I can add more to the diagram.

_ 7 _ _

3 4 5 _
W T F S

Notice that there is only one possible spot for 2. It cannot be on Monday because 3 is there, nor can it be on Saturday. It must be on Friday. This is why D is the correct answer. (Maybe our answer choices are mixed up. To be clear, the correct answer is "The second floor is examined on Friday.")

_ 7 2 _

3 4 5 8
W T F S

Because 2 must be on Friday, 8 must be on Saturday. 8 cannot be on Friday, which is why E is incorrect.