A particular seafood restaurant serves dinner Tuesday through Sunday.

A particular seafood restaurant serves dinner Tuesday through Sunday. The restaurant is closed on Monday. Five entrees snapper, halibut, lobster, mahi mahi, and tuna are served each week according to the following restrictions:
Halibut is served on three days each week, but never on Friday.
Lobster is served on one day each week.
Mahi mahi is served on three days each week, but never on consecutive days.
Halibut and snapper are both served on Saturday and Sunday.
Tuna is served five days each week.
No more than three different entrees are served on any given day.

Q: On which of the following pairs of days could the restaurant’s menu of entrees be identical?
A) Friday and Sunday
B) Tuesday and Wednesday
C) Saturday and Sunday
D) Wednesday and Friday
E) Thursday and Friday

Answer: D

Let’s try to make chart of each day

Halibut and snapper are both served on Saturday and Sunday.
and Halibut is served on three days each week, but never on Friday.
we don’t about other two days for Halibut. 

Mahi mahi is served on three days each week, but never on consecutive days.
so there is two case
case 1:


case 2:

Tuna is served five days each week.
but we can no serve Tuna  on Sunday because No more than three different entrees are served on any given day.
case 1:


case 2:

 

now we can fill only this much from given data.
so we try to eliminate options.

(A) Friday and Sunday
In both case Halibut is missing from Friday menu.
Hence A is not possible.

(B) Tuesday and Wednesday
(C) Saturday and Sunday
(E) Thursday and Friday 
In case of (B),(C) and (E) because they are are consecutive days.so we can not serve Mahi Mahi
Hence  (B),(C) and (E)  is not possible.

so remaining option (D) Wednesday and Friday is correct answer.

Q: Which of the following is a complete and accurate list of the days on which halibut and lobster may both be served?
A) Tuesday, Thursday
B) Tuesday, Wednesday, Thursday
C) Monday, Tuesday, Wednesday
D) Tuesday, Wednesday, Thursday, Friday
E) Tuesday, Wednesday, Thursday, Saturday

Answer: B

because halibut has to be serverd 3 daysshould be on Saturday and Sunday not on friday.
there may be chance of serving halibut on tue,wed,thurs if we consider two cases and each day should not exceed 3 food items.

Q: If mahi mahi is served on Saturday, it could be true that
A) snapper and mahi mahi are both served on Sunday
B) snapper and halibut are both served on Tuesday
C) lobster and halibut are both served on Thursday
D) tuna and snapper are both served on Saturday
E) lobster and snapper are both served on Friday

Answer: E

lobster and snapper are both served on Friday

Q: Which of the following statements provides sufficient information to determine on which three days halibut is served?
A) Mahi mahi and lobster are served on the same day.
B) Lobster and snapper are both served on Tuesday.
C) Tuna is served on Saturday, and lobster is served on Tuesday.
D) Mahi mahi is served on Saturday and snapper is served on all but one of the six days.
E) Tuna is served on Sunday, and snapper is served on Tuesday and Thursday.

Answer: E

Tuna is served on Sunday, and snapper is served on Tuesday and Thursday.