Question

Question of logical deduction #1

Answer 1

In the classroom, Ms Lam, Ms Chan and student A, B, C, D, E are playing games. Ms Lam gives 5 cards marked with 1-5 (natural number) to students A-E randomly so that every student has one card. Only the person who holds the card knows what the number of the card is.

Ms Lam : Student A, who has the card with the largest number?
Student A: I don't know
Ms Lam : Student B, Is the number of your card larger than that of C?
Student B: I don't know
Ms Lam : Student C, Is the number of your card larger than that of D?
Student C: I don’t know
Ms Lam : Student D, Is the number of your card larger than that of B?
Student D: ___________
Ms Lam : Student B, Is the number of your card larger than that of C?
Student B: No
Ms Chan: Ms Lam, I know what are the numbers on their cards now.

(a) What is the answer of D – Yes, No, or I don’t know?
(b) What are the cards student A, B, C, D, E are holding?

Answer 2

There must be some error Student B replies no and i don't know to same questions

Answer 3

If there is any error, then it would be my problem :S
But I think the question is correct. I just forget how to solve it

Answer 4

So far, I know A, B and C should not have the card 5 and the one who has the card 5 is E

Answer 5

and student B or C should not have the card '1'

Answer 6

that is easiest fact

Answer 7

I know :S

Answer 8

B has 2

Answer 9

D's answer should be I don't know.

Answer 10

question didn't have an error sorry

Answer 11

BTW, B has 2 :)

Answer 12

D doesn't get 4, Perhaps D gets 3
Sorry, have to go now. I'll check this when I come back

Answer 13

The only thing I'm stuck on, is why B has 2. Could someone quickly explain why?

Answer 14

Hmm... Since C answer => I don't know, so C doesn't get 1
Since B answered the last question with a 'No' probably B get a 2 (Besides, 1, 2 is the smallest)
Note that the answer of B, C, D are all 'I don't know'

Answer 15

Oh, A gets 1 :)

Answer 16

why

Answer 17

I see why B gets two now. Also, D doesn't get 5, so E gets 5, and not 1. We also know that D doesn't get 1. Thus, A must get 1.

Answer 18

So I can see that C gets 3, 4, and D gets 3, 4.

Why did you say D got 4?

Answer 19

Did I? I didn't!!!!!
''D doesn't get 4, Perhaps D gets 3''

Answer 20

I meant that -.-

Now I see why that's true though. So that means
A=1
B=2
C=4
D=3
E=5

Answer 21

Probably it's solved :)
Thanks!!!
(I did this question 3 years ago and I forgot how to do it 3 years later!!!!)

Answer 22

It's certainly a tough one.