Too much.

Regads

Why not option B ?

Because we care about of the authenticity to find our assumption. B talks about the appearance in his paintings.

Hope this helps.

Ask for further assistance if you do need.

Regards

option (B) is a close call : It states many, not all paintings -> what if one one painting has been found without the under-image; this may invalidate the option.
so (B) is not correct.

Please explain why not D?

D) A painted canvas cannot be reliably attributed to an artist unless the authenticity of any underimage that painting might contain can be reliably attributed to the artist.

The assumption is that even though another type of painting which is not made by Van Gogh would NOT contain an underlying image

D instead talks about any generally painted canvas which authenticity can not be attributed to another artist.

All that means: out of scope. We care about Van Gogh and the underlined image in his works.

Ask for further assistance.

Regards

Yeah, this argument passage is certainly on the harder side. It reminds me of exactly why I'm taking the GRE instead of the LSAT for law school. Fifty percent of the LSAT is made up of EXACTLY these kinds of questions (logical reasoning), and these questions are the sole reason why I'm taking the GRE rather than the LSAT. I take wayyy too long reading these things and trying to wrap my head around them that I would certainly run out of time on the LSAT. Thankfully, the GRE only has 1 or 2 of these types of questions in each Verbal section, and I always save them for very last.

I’m going to employ the methods from David Kiloran’s PowerScore Logical Reasoning Bible.

First you need to understand that the category belongs to the Justify the Conclusion group.

That said you need to break down the relevant premises and the conclusion.

Premise 1: Either van Gogh or another painter covered the first painting

In logical notation we denote “van Gogh painted the painting” as V and another “painter painted the painting” as P.

Thus the logical notation for Premise 1 is:

P —> V
V —> P

These are logical equivalent since they are contrapositives.

Conclusion: Because the face of the woman in the underimage also appears on canvases van Gogh is known to have painted, the surface painting must be an authentic self-portrait by van Gogh

Let “Woman in the under image also appears on canvases van Gogh is known to have painted” as W and “the surface painting must be an authentic self-portrait by van Gogh” is equivalent to “van Gogh painted the painting” so it is also V

Thus the logical notation for Conclusion is:

W —> V

So in summary we have:

P1: P —> V; V —> P
C: W—> V

We need another premise P2 that allows us to go from P1 to C.

The only premise that allows us to do this is W—>P because W—>P + P —> V = W—>P —> V = W —> V which is the conclusion C.

The only answer that has P2 is Answer choice C which is the logical contrapositive of P2:

“Any painted canvas incorrectly attributed to van Gogh would not contain an underimage of a subject that appears in authentic paintings by that artist.”

This is essentially saying P—>W which equals W—>P.

Although it may seem complicated based on what I wrote. If you understand the method and now how to break down the problem into logical steps you can breeze through this problem in about 30 seconds. I highly recommend that PowerScore book. It requires a learning curve to learn the logic, but the payoff is immense in terms of learning to dealing with any CR problem efficiently and easily.

In the argument presented, X-ray of painting reveals presence of underimage of women. He further makes conclusion that Because another painting that has similar kind of underimage, we can safely say that Original painting in question was painted by Van Gogh. Now to make this conclusion author must assume that(pre-thinking):
This is painting style that is only used by Van Gogh.
Keeping this in mind lets analyze options:
Quick analysis:
A. Naaaahhhh
B. May be
C. May be
D. This doesn't talks about if we can relate the painting in question to Van gogh or not. This is just a fact statement. So I won't pick this.
E. No.

Because B C are very close, we must call negation technique to finalize options.
Negate B: (None/less that 50%) painted canvases that can be reliably attributed to van Gogh contain underimages of subjects that appear on at least one other canvas that van Gogh is known to have painted.
If None of the paintings, which belong to Van Gogh, contains underimage: then conclusion breaks.....It is good
Just because we have "many paintings" written in option, there is another possibility to be evaluated: if some i.e. 1 or 2 paintings that is attributed to Van Gogh contains underimage, Conclusions strengthens....Nope This can not be our assumption.

Collected from GMAT club memeber sweetkriti

There is no reason in my opinion to collect the answers from GC.

We are an independent board though related.

provide your reasoning for the question independently. it is the best way to train

We do have also enough expert here to help you

Regards

Timer is missing on this question.

This was very tough. I thought about the explanation from different angles and I think this is the clearest one:

Reading only the question, the answer we are looking for is "This must be a Van Gogh painting if an underimage exclusively shows up under Van Gogh's painting."

B) Does not verify that the underimages exist exclusively under VG (Van Gogh).
Example: If there were 100,000 paintings of Queen Sarah's face and VG bought 1,000 of those paintings, just because we find 999 underimages of Queen Sarah's face in VG-certified paintings does not mean ALL unidentified paintings with Queen Sarah's underimage is VG. VG only owns a subset of Queen Sarah's paintings, so Queen Sarah's underimage cannot be used to authenticate VG paintings.

C) Is awkwardly, but intentionally phrased as a double-negative. It states that if we know for certain that an image is 1) NOT VG, and 2) does NOT contain an underimage that VG uses, then we know that the underimage is exclusive to VG. Which means we can use this underimage as a clue to validate the authenticity of a VG painting.