10 replies to this topic

[quicksand]

All coffeehouses and restaurants are public places. Most well-designed public places feature artwork. But if a public place is uncomfortable it is not well designed, and all comfortable places have spacious interiors.

My answer C) Most coffeehouses that are well designed feature artwork.

Credited Answer D) Any well-designed coffeehouse or restaurant has a spacious interior

I understand why the credited answer is right, but why is C not?

if All A are B

and most B which are D are C

then doesn't it follow that most A which are D are C ?

Thanks for your help

[rollinwiththehomies]

I got this question wrong too. Here is my explan. for why C is wrong:

Because "public places" is comprised of both coffeehouses and restaurants, it could be that only 2% of well-designed coffeehouses feature artwork, and 98% of well-designed restaurants feature artwork. So the statement ("most well-designed public places features artwork") still holds true as 98% of public places feature artwork, but choice C is false as most of the coffeehouses do not.

That is...
we cannot equate "Most well-designed public places feature artwork" with "most well-designed coffeehouses feature artwork".

I hope i'm right with this explanation

[quicksand]

Just got this response from my old instructor:





For the following inference question, I don't understand why my answer isn't correct, thought I do understand why the credited answer is.



All coffeehouses and restaurants are public places. (All Lamborghinis and Rolls-Royces are cars.) Most well-designed public places feature artwork. (Most new cars cost less than $40,000.) But if a public place is uncomfortable it is not well designed, and all comfortable public places have spacious interiors.



My Answer: C) Most coffeehouses that are well designed feature artwork. (Most Lamborghinis that are new cost less than $40,000.)

Makes sense... All A are B doesn't mean all B are A...

[yoni45]

Yup, that's essentially correct. You can actually take that a number of steps further too:

You know that most 'well designed public places' feature artwork, but public spaces aren't limited to coffeehouses or restaurants. Yes, it's true that coffeehouses and restaurants are public spaces, but what about parks? museums? monuments? movie theaters?

There could be countless other public spaces, so even if 'most well-designed public spaces have artworks' that entire majority could be covered by all those other things.

If you want to look at it mechanically, you can only 'transfer' a most statement if it's the first one in the chain (same applies to some statements). That is:

"Most A's are B's, and all B's are C's" absolutely does mean that most A's are C's.

However,

"All A's are B's, and most B's are C's" does not mean that most A's are C's.

Hope this helps! =)

rollinwiththehomies, on 30 January 2012 - 02:20 PM, said:

I got this question wrong too. Here is my explan. for why C is wrong:

Because "public places" is comprised of both coffeehouses and restaurants, it could be that only 2% of well-designed coffeehouses feature artwork, and 98% of well-designed restaurants feature artwork. So the statement ("most well-designed public places features artwork") still holds true as 98% of public places feature artwork, but choice C is false as most of the coffeehouses do not.

That is...
we cannot equate "Most well-designed public places feature artwork" with "most well-designed coffeehouses feature artwork".

I hope i'm right with this explanation

[KER_2012]

Thanks for this! I was reviewing this question earlier today and was having the exact same issue. It makes so much more sense now.

[BlondeLiv29]

Where is this question? I would like to look at the whole thing.

[yoni45]

PT65, S1, Q25 =)

[BlondeLiv29]

Thanks! how did you all know exactly what the op was looking at? Are you working together on certain pt's?

[Catalyst]

BlondeLiv29, the OP posted the question and others identified the flaw & showed how they got to the "right" answer. You don't really need to have any additional context to work through it.

As for Yoni, he's a tutor/prep course instructor. I bet he didn't even have to look up where that question was...

Edited by Catalyst, 02 February 2012 - 10:15 AM.

[Jaspri]

I'm such an LSAT geek...I found a similar question and it stumped me on a PT I was doing yesterday. Going over it, slowly, I see now the error. But here it is for anyone who wants more practice with these types...I believe it's a PT in the 40s...the copy I printed out didn't have a label....

Here it is:

Most lecturers who are effective teachers are eccentric, but some noneccentric lecturers are very effective teachers. In addition, every effective teacher is a good communicator.

Which of the following statements follows logically from the statements above:

A) Some good communicators are eccentric
B) All good communicators are effective teachers
C) Some lecturers who are not effective teachers are not eccentric
D) Most lecturers who are good communicators are eccentric
E) Some noneccentric lecturers are effective teachers but are not good communicators

[Jaspri]

I picked C but the answer is A. I diagrammed it as follows:

ET (effective teacher) -----------> EC (eccentric)
(most)

NotEC -------------> ET
(some)

ET --------> GC (good communicator)

You can make a better chain connecting everything with a pencil...I don't have the computer know-how to do it on screen