Discussion
If T's appointment is immediately after P's appointment and immediately before W's appointment, then which one of the following must be true?
*This question is included in Sequencing: Lesson Set 1 (of 5) - Intro, question #5
| (A) | W's appointment is at some time before R's appointment. |
| (B) | ... |
| (C) | ... |
| (D) | ... |
| (E) | ... |
| (F) | ... |
The solution is
Posted: 10/04/2012 23:50
It seems like it is possible to have a sequence that progresses as follows: U P T Q S R W
in this case, P is before R and answer D would not be the case. (?)
in this case, P is before R and answer D would not be the case. (?)
Posted: 10/05/2012 15:02
P Q R S T U V W
from the statements, we can arrange one scenario when T has slot 3:
__ _P_ _T_ _W_ ___ ___ ___
1 2 3 4 5 6 7
Since Q < W and U < P, this scenario is not feasible, because we can't fit Q and U both in slot 1.
The other scenarios are if R has appointment 3:
__ _S_ _R_ ___ ___ ___ ___
1 2 3 4 5 6 7
__ ___ _R_ _S_ ___ ___ ___
1 2 3 4 5 6 7
In either sub-case, we have to be able to fit the sequence P-T-W, taking up 3 slots. That is, PTW must be after R or after RS, occupying any 3 slots in 4-5-6-7 in the first sub case, or 5-6-7 in the 2nd sub-case.
So, D.
from the statements, we can arrange one scenario when T has slot 3:
__ _P_ _T_ _W_ ___ ___ ___
1 2 3 4 5 6 7
Since Q < W and U < P, this scenario is not feasible, because we can't fit Q and U both in slot 1.
The other scenarios are if R has appointment 3:
__ _S_ _R_ ___ ___ ___ ___
1 2 3 4 5 6 7
__ ___ _R_ _S_ ___ ___ ___
1 2 3 4 5 6 7
In either sub-case, we have to be able to fit the sequence P-T-W, taking up 3 slots. That is, PTW must be after R or after RS, occupying any 3 slots in 4-5-6-7 in the first sub case, or 5-6-7 in the 2nd sub-case.
So, D.
Posted: 10/05/2012 20:32
Thanks for your response. However, I am not clear as to why W must appear immediately after P and T. Q and U don't need to come before both W and P.
Thus, if the order in this case is:
U P T R S Q W
it seems all the rules are being followed.
PT form a block as is stipulated by the question.
U comes before P
Q comes before W
T takes up appointment 3
And SR form a block.
This allows P to come before R.
I'm most likely missing something. Can you help point it out? Thanks.
Thus, if the order in this case is:
U P T R S Q W
it seems all the rules are being followed.
PT form a block as is stipulated by the question.
U comes before P
Q comes before W
T takes up appointment 3
And SR form a block.
This allows P to come before R.
I'm most likely missing something. Can you help point it out? Thanks.
Posted: 10/05/2012 20:40
Jina, you are missing the statement right before the choices, which explicitly says: "If T's appointment is immediately after P's appointment and immediately before W's appointment, ...", hence we are constrained by an additional condition that P-T-W needs to appear consecutively.
In problems like this (sequencing), it is best to diagram the scenarios like I did, including the sub-scenarios, so you can rule out the invalid ones, and zoom in on the feasible ones.
In problems like this (sequencing), it is best to diagram the scenarios like I did, including the sub-scenarios, so you can rule out the invalid ones, and zoom in on the feasible ones.
Posted: 10/05/2012 20:42
I completely missed that. Thanks Joel.
Posted: 11/17/2012 15:56
Can you help me understand why U doesn't have to be prior to R? If the order P,T,W must hold then both Q and U must be ahead of that group. (Q before W and U before P) If that's true, S can't occur ahead of R because you'd need 3 letters, S,Q, and U before R and only 2 spots.
U or Q, R, S, P, T, W
U before R & R before P?
U or Q, R, S, P, T, W
U before R & R before P?
Posted: 11/18/2012 04:07
Carl,
First we'll set the conditions into definitions:
Def. 1 Q < W
Def. 2 U < P
Def. 3 ( R || T ) == 3rd
Def. 4 ( SR ) || ( RS )
Def. 5 ( PTW )
We have 7 slots AND 7 different symbols to set, first we look at our definitions for constants with respect to position, definition 3 targets constant location, thus:
1 2 3 4 5 6 7
- - R
- - T
Def. 5 takes three consecutive slots this limits the placement to:
- P T W
- - R P T W
- - R - P T W
Def. 1 and 2 force the 5th definition PTW to have Q and U before it thus T as 3rd is not an option since there's only one slot in front, so now we have:
1 2 3 4 5 6 7
- - R P T W
- - R - P T W
Now we implement def. 4 ( SR || RS )
- S R P T W - >>> only one spot before PTW thus no option
- S R - P T W
- - R S P T W
Thus the valid sequences are:
seq. 1 U S R Q P T W
seq. 2 Q S R U P T W
seq. 3 U Q R S P T W
seq. 4 Q U R S P T W
Answer A. W < R always false
Answer B. U < R see seq. 2 thus false
Answer C. S < U see seq. 1, 3 and 4 thus false
Answer D. R < P always true
Answer E. Q < S see seq. 1 thus false
Niels
First we'll set the conditions into definitions:
Def. 1 Q < W
Def. 2 U < P
Def. 3 ( R || T ) == 3rd
Def. 4 ( SR ) || ( RS )
Def. 5 ( PTW )
We have 7 slots AND 7 different symbols to set, first we look at our definitions for constants with respect to position, definition 3 targets constant location, thus:
1 2 3 4 5 6 7
- - R
- - T
Def. 5 takes three consecutive slots this limits the placement to:
- P T W
- - R P T W
- - R - P T W
Def. 1 and 2 force the 5th definition PTW to have Q and U before it thus T as 3rd is not an option since there's only one slot in front, so now we have:
1 2 3 4 5 6 7
- - R P T W
- - R - P T W
Now we implement def. 4 ( SR || RS )
- S R P T W - >>> only one spot before PTW thus no option
- S R - P T W
- - R S P T W
Thus the valid sequences are:
seq. 1 U S R Q P T W
seq. 2 Q S R U P T W
seq. 3 U Q R S P T W
seq. 4 Q U R S P T W
Answer A. W < R always false
Answer B. U < R see seq. 2 thus false
Answer C. S < U see seq. 1, 3 and 4 thus false
Answer D. R < P always true
Answer E. Q < S see seq. 1 thus false
Niels