Exam 2009

So...what did you all think?
I thought it was ok. I messed up on 2 of the formal proof questions, got stressed about time, started rushing and making stupid mistakes that required a lot of erasing.
Wasn't sure about the first question either, they asked which two were false. I wrote 1.1-1.8 and specified which were true and which were false(only 2 of course).

Hope I did enough to pass anyway...then onto Formal Logic 3!

Well have 15min to spare (not a good thing). Felt like I wasn't giving enough for the marks.

Question1: Listed them 1 -8 (True/False)
Question2: Didn't see the MoreThan for the rose's
Question3: Gave a word for word translation then a common English translation e.g If Blah x then Blah y i.e Blah Blah.
Question4: Aaargh....DNF...Please can someone make a model answer.
Question5: Easy (I hope ) Truth tables yay!
Question6: Piet is not necessarily honest, difference between "if" and "if and only if" I hope.
Question7: Lots of marks, but I didn't write a lot. You guys?
Question8: Everything came out to the conclusions hope how I got there was enough.
Question9: A || B contradicts ~A && ~B. I didn't do a long proof, probably about 10 lines. You guys?
Question10: At most 2 and exactly 2. Can some on give us the answer. I think I got it right.

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"Flying is learning how to throw yourself at the ground and miss." - Douglas Adams
"Time is a great teacher, but unfortunately it kills all its pupils ..." - Louis Hector Berlioz
I think animal testing is a terrible idea; they get all nervous and give the wrong answers.

I thought the exam was easy.

Although I put 6&7 for question 1. In my opinion, 6 was definately false. Wasnt sure about 7.
I think the sentence was that for all values x, if x is Tet, then for all y, y is not large. And there was a tet, as well as a large object.

Q2: Not too bad
Q3: easy
Q4: Easy. ended up with (!A and !B and D) or (C and D) <- or something like that.
Q5: Easy
Q6: Said invalid. The conclusion couldnt possibly follow from the premise.
Q7: It was easy to show each kid was each others sibling.
Q8: First one easy, second one I left out (I aint good at quantifier proofs)
Q9: Easy, saw this before somewhere. Probably notes.
Q10: Not too bad

More or less the same boet, if u basically nailed question 1-7, you got the marks!!! im hopeless at question 9 and 10. and 8.2 also. 8.1 was already given

Q1 - The 2x Between() predicates were wrong for me. You could not draw a straight line to the points for the plain Between() and the quantified between had a condition that all Tets had a cube to the left of it, and one Tet was on the leftmost column, so false there. There was tricky one though, which looked completely false, until you saw there wasn't a block in the world for it, making it true.

Q2 - Was alright, quite fun, but I never know if I screw these up, hehe.

Q3 - Roughly converted "word for word" in the rough work, then turned them into proper English sentences in the answer.

Q4 - This was easy for me, but I got to a completely different answer than Scag. I didn't use Distributivity over ^, which looks like what he did. Just DeMorgan, Negation elim, DeMorgan again, Commutativity, then Dist. over v, and I got to a Disjunct of 2 Conjunctions.

Q5 - This is always a breath of fresh air. Got the tautology.

Q6 - It was valid, but unsound. The premises made the conclusion plausible, however it is equally plausible that he is a dishonest politician.

Q7 - This I didn't have a problem with, used Proof by Cases

Q8 - first one was easy, second one I got to the conclusion. Used ^ intro and modus pollens quite a bit here and then just 'E' intro.

Q9 - Was quite nice, just a subproof of each disjunct with a ^ elim of the first premise proved a contradiction with v elim.

Q10 - Definitely got the first part right, and I think the second part was also right.

And then had to write INF206 right after. Quite the mind shift

I thought the paper was quite fair.
So far, it's the easiest paper I have had.
I think I messed up a little with the formal proofs.

With the Piet being honest argument, I answered it as being invalid.
Even with the premise of all car salesmen are dishonest being true and Piet not being a carsalesman being true, it is possible for Piet being honest to be false... the first premise states who is dishonest ( car salesmen) and that Piet is not a car salesman... No premise mentions which group is honest. It mentions which group is dishonest, and by Piet not being part of this group, it does not mean that he is part of the honest group. He could be part of another trade (not car sales) which is also dishonest. Therefore the argument is invalid.

Understand the reasoning there. I just remember the past paper question with Meryl Streep, and based myself on that. TBH both make sense to me. However, I also thought 8 marks was too easy to say the argument was simply invalid. Hope my paranoia didn't get the better of me

I argued the same as Leila, except I took it that he was a new (as opposed to a used car salesman in premise 1) car salesman. But I also mentioned that he could possibly be a corrupt police chief, or any other dishonest trade.

Yes, but that would depend on the domain of disclosure. As far as Piet goes, according to what we have, Piet is honest. It is a Valid argument, but not a Sound one. (also thought of Merryl Streep exersise).

Validity -> IMPOSSIBLE for the premises to be true and the conclusion false. I think Piet could be Dishonest or not Dishonest. Nothing states that not being a car salesman will result in you being honest. You may be a politician

x -> y if Saleman then dishonest
z = ~x Piet not a salesman

z = ~y therefore not dishonest

as stated ~x = ~y (~x=z=~y) , but ~x || y (equiv to x->y). We have said ~x in prem 2, but the statement (~x || y) can still be true if y or ~y. So Piets honesty (y) is not effected by the premises in regards to not being a salesman (~x). Therefore the conclusion of z = y or z = ~y are both possible and it means the conclusion CAN be false (z=~x = y as apposed to z=~x =~y) and premises true. i.e the argument is invalid.

Soundness -> Needs to be a valid argument, and it's premises true. So assuming it's premises are true, it's still not sound, as by validity.

Well that's what I think..Feel free to tear it apart. Only constructive criticism welcome

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"Flying is learning how to throw yourself at the ground and miss." - Douglas Adams
"Time is a great teacher, but unfortunately it kills all its pupils ..." - Louis Hector Berlioz
I think animal testing is a terrible idea; they get all nervous and give the wrong answers.

Looks like we all have our own ideas

Normally, that would be a good thing.