继续复习预防2月补考,结果prep59卡了下-.-谁来帮忙解答下

taoransk · 发表于 2010-12-15 21:23:10

Alicia will take exactly four courses this semester. She must choose from the following seven courses -- Geography, Japanese, Macroeconomics, Psychology, Russian, Statistics (Which is offered twice, once each on Tuesdays at 9AM and 3PM), and World History. No one is allowed to take any course more than once per semester. Because of university requirements and time conflicts, the following restrictions apply to Alicia's choices:
-- She must take Japanese if she does not take Russian
-- She cannot take Japanese if she takes Macroeconomics
-- She cannot take World History if she takes Statistics at 9AM
-- She must take either Geography or World History but cannot take both

13. Which courses Alicia takes is fully determined if she takes Russian and which one of the following?
(A) World History
(B) Statistics
(C) Psychology
(D) Macroeconomics
(E) Japanese

15. If alicia takes Statistics at 3PM and Geography, then which one of the following courses must she also take?
(A) Japanese
(B) Macroeconomics
(C) Psychology
(D) Russian
(E) World History

16. Suppose that Alicia must take Statistics if she takes Psychology, but rather than being restricted to taking Statistics at 9AM she can take it at either 9AM or at 3PM. If all the other restrictions remain the same, then which one of the following could be the list of the four courses Alicia takes?
(A) Psychology, Russian, Statistics, World History
(B) Macroeconomics, Psychology, Statistics, World History
(C) Macroeconomics, Psychology, Russian, World History
(D) Geography, Psychology, Russian, World History
(E) Geography, Macroeconomics, Russian, World History

求整体题干之推理步骤, 并以上诸题之解题思路及详细分析

临表涕淋, 顿首拜上

sdcar2010 · 发表于 2010-12-16 11:29:17

G J M P R S(3) S(9) H Total 8 classes

~R --> J
M --> ~J
S(9) --> ~H
P --> S(9)
G --> ~H
~G --> H

Frame 1
In: (G) (_) (_) (_) | Out: (H) (_) (_) (_)

Frame 2
In: (H) (R) (S(3)) (M/J) | Out: (G) (S(9)) (P) (J/M)

sdcar2010 · 发表于 2010-12-16 11:44:40

13. Which courses Alicia takes is fully determined if she takes Russian and which one of the following?
(A) World History
(B) Statistics
(C) Psychology
(D) Macroeconomics
(E) Japanese

Apparently if you use Frame 2, none of the choices will give your a definite arrangement due to the (M/J) constraint. So let's go with Frame 1, which is:
In: (G) (R) (_) (_)
Then with answer (C), P --> S(9) --> ~H, you got the next two blanks filled without compromising G.

sdcar2010 · 发表于 2010-12-16 11:51:48

15. If alicia takes Statistics at 3PM and Geography, then which one of the following courses must she also take?
(A) Japanese
(B) Macroeconomics
(C) Psychology
(D) Russian
(E) World History

Since she takes both S(3) and G, we need to use Frame 1:
In: (G) (S(3)) (_) (_) | Out: (H) (S(9)) (_) (_)
~S(9) --> ~P, and we know that only one from J and M can be chosen, so R has to be taken as well.
In: (G) (S(3)) (J/M) (R) | Out: (H) (S(9)) (M/J) (P)
So D is the answer.

sdcar2010 · 发表于 2010-12-16 11:59:36

16. Suppose that Alicia must take Statistics if she takes Psychology, but rather than being restricted to taking Statistics at 9AM she can take it at either 9AM or at 3PM. If all the other restrictions remain the same, then which one of the following could be the list of the four courses Alicia takes?
(A) Psychology, Russian, Statistics, World History
(B) Macroeconomics, Psychology, Statistics, World History
(C) Macroeconomics, Psychology, Russian, World History
(D) Geography, Psychology, Russian, World History
(E) Geography, Macroeconomics, Russian, World History

Since this is a rule change, let's list the rules again:
G J M P R S(3) S(9) H Total 8 classes

~R --> J
M --> ~J
S(9) --> ~H
P --> S(9) or S(3)
G --> ~H
~G --> H

(A) Psychology, Russian, Statistics, World History
(B) Macroeconomics, Psychology, Statistics, World History [M --> ~J; ~J --> R; but there is no R]
(C) Macroeconomics, Psychology, Russian, World History [P --> S(3) or S(9); but there is no S]
(D) Geography, Psychology, Russian, World History [G --> ~H; but there is H]
(E) Geography, Macroeconomics, Russian, World History [G --> ~H; but there is H]

So A is the answer!

taoransk · 发表于 2010-12-16 13:03:18

Thx a lot ! ^^ seems I need get some improment on this area, which is kinda weakeness for me. haha

well, hope I don't need another test, but still, prepare is always needed

继续复习预防2月补考,结果prep59卡了下-.-谁来帮忙解答下

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