Do I Need to Include All Variables in This Boolean Logic Statement?

[rokimomi]

Homework Statement

let p, q, and r be the following propositions

p: You get an A on the final exam.
q: You do every exercise in this book
r: You get an A in this class

translate: You get an A on the final, but you don't do every exercise in this book; nevertheless, you get an A in this class.

Homework Equations

The Attempt at a Solution

Do I have to include the part about doing exercises at all? Since it's sufficient enough to have p\rightarrowr to convey the message? What I'm worried about is if they want us to include it anyways so someone can go from this logic to English again. How would I include q then?

I would assume that

 

[story645]

Do I have to include the part about doing exercises at all?

Yes, because it has a truth value and therefore affects the truth value of the whole sentence.
But is a conjunction, so logically/grammatically it works the same way as an and.

 

[rokimomi]

How about ((p\wedgeq)\vee(p\wedge\negq))\rightarrowr

Is there any way to convey this simpler?

 

[story645]

How about ((p\wedgeq)\vee(p\wedge\negq))\rightarrowr

Is there any way to convey this simpler?

Using distrbutive properties, you end up with :
(p\wedge(\negq\veeq))\rightarrowr, which is back to p\rightarrowr, which again means a loss of the but clause.

 

[rokimomi]

Wait, wasn't that my goal though? Something that simplifies to "if p then q".

Hm, I am rereading it again, and I am getting the feeling that I should just word for word put it into logic. So

(p\wedge\negq) \rightarrow r

So is their use of "but" just to confuse me?

 

[story645]

So is their use of "but" just to confuse me?

Probably.

Hm, I am rereading it again, and I am getting the feeling that I should just word for word put it into logic.

That's my usual assumption with these types of problems.

 

[rokimomi]

Oh wow, I over-read your comment about "but" the first time through. Sorry bout that and thanks for the help.

 

[cepheid]

Hm, I am rereading it again, and I am getting the feeling that I should just word for word put it into logic. So

(p\wedge\negq) \rightarrow r

Yeah, exactly right.

So is their use of "but" just to confuse me?

No, it's standard english. 'But' is the right conjunction to use, because the clause that comes after it is a negative, and tends to have the effect of lessening the impact of the first. It was your job to figure out that this sentence given in proper english is logically equivalent to:

"You get an A in the final exam and you do NOT do every exercise in the book..."

and you did figure it out. If somebody had said either wording to you, you would have understood what he meant.