Which one of the following statements must be true?
Anna20on August 19, 2020
Doctor Yamata
Why is the correct answer here not C? What is the process for solving this question?
In my set up, Doctor Yamata has to treat patients in the afternoon on Saturday and conduct research on Saturday morning - because we can't have lecturing or operating on Saturday and it has to match the numerical distribution.
I think can see why E is correct too - but what am I missing with C? Thanks so much!
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We know that Dr. Y works five days of the week: M, T, W, F, and S.
On these days, she performs four different activities: L, O, P, and R.
She performs exactly one activity in the morning and exactly one activity in the afternoon.
AM: _ _ _ _ _
PM: _ _ _ _ _
M T W F S
Now let's go through our conditions.
Rule 1 - Dr. Y performs O exactly three mornings during the week.
Rule 2 - If Dr. Y performs O on M, she does not perform O on T.
OM --> Not OT
OT --> Not OM
Rule 3 - Dr. Y does L in the afternoon on exactly two consecutive calendar days.
Rule 4 - Dr. Y treats P on exactly one morning and exactly three afternoons.
Rule 5 - Dr. Y conducts R on exactly one morning.
Rule 6 - Dr. Y neither does L nor performs O on Saturday.
This means that Dr. Y can only conduct R or treat P on Saturday.
We now know the activities which must take up all 10 slots of Dr. Y's time during the week. We just don't know what order they go in.
Morning Activities: O O O P R
Afternoon Activities: L L P P P
We do know that Dr. Y cannot perform O on S and Rule 2 tells us that she cannot perform O on both M and T. Therefore, we have two options for Dr. Y's mornings.
Option 1
AM: O R/P O O P/R
M T W F S
Option 2
AM: R/P O O O P/R
M T W F S
We also know that Dr. Y does L in the afternoon on exactly two consecutive days which cannot be Saturday. Therefore, we have three options.
Option 1
PM: L L P P P
M T W F S
Option 2
PM: P L L P P
M T W F S
Option 3
PM: P P L L P
M T W F S
We are looking for the answer choice which MUST be true.
Answer choice (C) could be true, but it does not have to be true. Why? Because pairing Option 1 AM and Option 1 PM gives us a schedule where Dr. Y does not conduct R on a day where she treats P. Notice that there is nothing that says Dr. Y must perform two different activities each day. Therefore, there is no reason why Dr. Y cannot treat P all day Saturday.
AM: O R O O P
PM: L L P P P
M T W F S
The only day on which Dr. Y conducts R is a day when she does L. Notice that this meets all of our conditions:
1) Dr. Y performs O on M, W, and F mornings.
2) Dr. Y performs O on M and does not perform O on T.
3) Dr. Y does L on M and T afternoons.
4) Dr. Y treats P on F morning and on W, F, and S afternoons.
5) Dr. Y conducts R on T morning.
6) Dr. Y only treats P on S; she neither does L nor performs O on this day.
On the other hand, answer choice (E) must be true because it is impossible to design a schedule where Dr. Y does not L on the same day that she performs O.
