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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
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alphaseeker wrote:
For over two centuries, no one had been able to make Damascus blades—blades with a distinctive serpentine surface pattern—but a contemporary sword maker may just have rediscovered how. Using iron with trace impurities that precisely matched those present in the iron used in historic Damascus blades, this contemporary sword maker seems to have finally hit on an intricate process by which he can produce a blade indistinguishable from a true Damascus blade.

Which of the following, if true, provides the strongest support for the hypothesis that trace impurities in the iron are essential for the production of Damascus blades?


(A) There are surface features of every Damascus blade—including the blades produced by the contemporary sword maker—that are unique to that blade.

(B) The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.

(C) Almost all the tools used by the contemporary sword maker were updated versions of tools that were used by sword makers over two centuries ago.

(D) Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted.

(E) Although Damascus blades were renowned for maintaining a sharp edge, the blade made by the contemporary sword maker suggests that they may have maintained their edge less well than blades made using what is now the standard process for making blades.


Passage analysis
For over two centuries, no one had been able to make Damascus blades—blades with a distinctive serpentine surface pattern—but a contemporary sword maker may just have rediscovered how.
    Damascus blades are blades with a special snakelike surface design.
    No one has been able to make such blades for over two centuries.
    We can infer that Damascus blades stopped been made over two centuries ago.
    But a modern-day sword maker seems to have found a way to make the blades again.
Using iron with trace impurities that precisely matched those present in the iron used in historic Damascus blades,
    The sword maker used iron with trace impurities which were exactly the same as found in the Damascus blades.
this contemporary sword maker seems to have finally hit on an intricate process by which he can produce a blade indistinguishable from a true Damascus blade.
    This formula seems to have finally enabled the sword maker to make blades that cannot be distinguished as different from the real ones.

Conclusion
Trace impurities in the iron are essential for the production of Damascus blades

Prethinking
Strengthen Framework
Now per our understanding of the passage, let’s first write down the strengthen framework:

What new information will help us believe more in the conclusion
Trace impurities in the iron are essential for the production of Damascus blades


Given that
For over two centuries, no one had been able to make Damascus blades
A modern-day sword maker seems to have rediscovered the lost art of making Damascus blades.
He uses iron with trace impurities that matched those present in the historic blades.
He apparently makes blades that cannot be differentiated from a real Damascus blade.

Thought process

The entire argument is full of words that imply “seems”. He may have discovered and seems to have hit on a process indicate uncertainty.

But if some evidence could be found to show that it is indeed so it would strengthen the argument.

The points to ponder over are:

The blades had been stopped being made two centuries ago. There must have been some reason for the art to get lost.
Why does the sword maker need to use iron with trace impurities?

Strengthener

Most likely the iron used to make the blades over two centuries ago was of some special type which was no longer available.

And that is why the blades were not produced anymore.

And the sword maker had to add the impurities to make the blades resemble the real ones in every aspect.

So, if any option suggests that the iron from which the real blades were made had ceased to be available over two centuries ago, then it will strengthen the hypothesis.

Answer Choice Analysis
Option A

This just supports the fact that the sword makers blades cannot be distinguished from the real ones. It does not offer any new information.
Thus, this is not the correct choice.

Option B

Even if the source of iron of the contemporary blade was not known centuries ago, the sword maker ensured that the composition matched with the iron used centuries ago to make the Damascus blades. This option fails to support the conclusion that the sword maker had to add the trace impurities.
Thus, this is not the correct choice.

Option C

This option is about updated tools and not replicas of tools made over two centuries ago. So, it is irrelevant to the argument.
Thus, this is not the correct choice.

Option D

This is in line with our pre-thinking.
This supports the theory that the trace impurities found in that iron were necessary to the making of the blades.
Thus, this is the correct answer choice.

Option E

Whatever be the process of making and maintain the two kinds of blades, the fact is they are indistinguishable from each other. It fails to offer any support to the conclusion about the necessity of adding trace impurities.
Thus, this is not the correct choice.
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
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Over 2 centuries - No one has been able to make DB(damascus blade)
Contemp swrd mkr has rediscovered how to make
Iron + TI(trace impurities) --> Produce a blade similar to a true DB.

We have to strengthen the argument.

Prethink: There was some requirement for adding the trace impurities to make it appear original.

D aligns with the prethinking.

Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted - The iron which was exquisitely used in the DB got exhausted. So in order to replicate the properties of the iron used in DB, some impurities are added now to the currently available iron. This strengthens the argument.
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
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Conclusion : Trace impurities are essential to Damascus blades.

if Damascus blades, then Trace impurities.

if no trace impurities , then no Damascus blades.

D just states this contrapositive.
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
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Here we need to support the hypothesis that trace impurities in the iron are essential for the production of Damascus blades

This is cause and effect pattern problem. Here

Cause: Impurities in iron
Effect: Damascus blade.

So to strengthen it we can say that

1. no cause ---> no effect
2. whenever cause ---> effect
3. effect did not cause the cause.

D fits the first pattern i.e. no impurities in iron ---> no damascus blade
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
I am still NOT convinced why option D is the correct answer. Can someone explain this option in more detail? Also, option B as well, as I picked B as the answer. (Reason for picking B : as I eliminated all the other options)

For over two centuries, no one had been able to make Damascus blades - blades with a distinctive serpentine surface pattern - but a contemporary sword maker may just have rediscovered how. Using iron with trace impurities that precisely matched those present in the iron used in historic Damascus blades, this contemporary sword maker seems to have finally hit on an intricate process by which he can produce a blade indistinguishable from a true Damascus blade.

Which of the following, if true, provides the strongest support for the hypothesis that trace impurities in the iron are essential for the production of Damascus blades?

A) There are surface features of every Damascus blade-including the blades produced by the contemporary sword maker-that are unique to that blade.
B) The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.
C) Almost all the tools used by the contemporary sword maker were updated versions of tools that were used by sword makers over two centuries ago.
D) Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted.
E) Although Damascus blades were renowned for maintaining a sharp edge, the blade made by the contemporary sword maker suggests that they may have maintained their edge less well than blades made using what is now the standard process for making blades.

My Understanding :
Option D : Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted
This option is talking about sword makers' original source of iron, which was used for making the D-blades. But we are not concerned with the source of iron, we have to support that trace impurities in the iron are essential for the production of Damascus blades. Just by knowing the source, we cannot predict that the impurities are essential?? That's why I rejected this option.

The question that comes after reading option D is that Damascus blades could not be produced from iron that was from some other sources. Otherwise the production could have continued. So, there is something different in the iron that is obtained from the original source as compared to the iron from the other available sources. What could be that difference?? :?: :?: :?: :? :?

After further thinking :idea: :idea: , that difference can be something other than impurities as well. Then, how does option D strengthens?? :?: :?: :?: :?: :?:

Option B : The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.
Even this option is talking about the source of iron. :shock: But the source of iron with which the contemporary sword maker made Damascus blades. This source of iron was unknown when sword makers of the past made Damascus blades. So, if this source of iron was known at that time, then Production of Damascus blades by sword makers of the past might not be ceased abruptly. As using this source of iron the contemporary sword maker made Damascus blades; This supports the conclusion. The trace impurities in the iron are essential for the production of Damascus blades : these impurities are present in this source of iron, that's why cont. sword maker was able to make the D-blades.

Can someone review my explanation? mikemcgarry chetan2u chiranjeev VeritasPrepKarishma

Originally posted by vnigam21 on 10 Aug 2017, 01:02.
Last edited by vnigam21 on 10 Aug 2017, 01:46, edited 1 time in total.
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn, sayantanc2k,
I am afraid i am still confused.
Honestly speaking, i did picked up B, my reasoning is as following:

The conclusion is : trace impurities in the iron are essential for the production of Damascus blades.
My interpretation of "essential" is necessary, it is impossible to produce Damascus blades without trace impurities. in a short, no trace impurities, no production.

per answer choice B, The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.
1) if B is true, the source was unknown two centuries ago, in other words, no source,
2) as the prompt says, no one had been able to make Damascus blades, in other words , no production.
based on 1) and 2), no source, no production.

Per answer choice D, Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted
it is also "no source, no production".

I know there is impossible have two answer choice on GMAT. So i picked up randomly.
I known i am wrong, but i have no idea where is incorrect
Please help clarify,
Thanks in advance

Have a nice day
>_~
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
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zoezhuyan wrote:
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn, sayantanc2k,
I am afraid i am still confused.
Honestly speaking, i did picked up B, my reasoning is as following:

The conclusion is : trace impurities in the iron are essential for the production of Damascus blades.
My interpretation of "essential" is necessary, it is impossible to produce Damascus blades without trace impurities. in a short, no trace impurities, no production.

per answer choice B, The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.
1) if B is true, the source was unknown two centuries ago, in other words, no source,
2) as the prompt says, no one had been able to make Damascus blades, in other words , no production.
based on 1) and 2), no source, no production.

Per answer choice D, Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted
it is also "no source, no production".

I know there is impossible have two answer choice on GMAT. So i picked up randomly.
I known i am wrong, but i have no idea where is incorrect
Please help clarify,
Thanks in advance

Have a nice day
>_~


Hi zoezhuyan!

Happy to help :-)

First of all, great job narrowing down the essential parts of the argument! As you said, the key here is "no trace impurities, no production". In order to have those trace impurities, we either need the same source of iron as the original, or a similar source of iron with the same impurities.

Now, choice B says that the source of iron that was used in the new blades was unknown two centuries ago, when the old blades were made. This is actually the opposite of what we want. Remember that in order to make this blade, we need the same source of iron, or a similar one. If the iron used in the new blades was unknown when the original blades were made, then it probably isn't the same source, with the same impurities. So B actually weakens the argument, not strengthens it, since it basically tells us that the iron sources made to create the blades were not the same, and therefore likely did not have the same trace impurities (or at the very least, we don't know whether or not they did).

So D is the correct answer :-)

Does that make sense? If not, let me know! :-)
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
AndrewN VeritasKarishma

We are asked to strengthen the fact that impurities are essential for making Damascus blades.

I have a question.

'Using iron with trace impurities'
I thought that trace impurities were added to the iron by the sword maker while making the DM blades.Therefore, I marked B as an answer.

In option B , since the form of iron was unknown centuries ago, the deciding factor would have been impurities added by the sword maker.

Where am I going wrong??
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Re: For over two centuries, no one had been able to make Damascus blades—b [#permalink]
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warrior1991 wrote:
AndrewN VeritasKarishma

We are asked to strengthen the fact that impurities are essential for making Damascus blades.

I have a question.

'Using iron with trace impurities'
I thought that trace impurities were added to the iron by the sword maker while making the DM blades.Therefore, I marked B as an answer.

In option B , since the form of iron was unknown centuries ago, the deciding factor would have been impurities added by the sword maker.

Where am I going wrong??


Think about what this means in the argument:

Using iron with trace impurities that precisely matched those present in the iron used in historic Damascus blades ...

The blade maker analysed the impurities in the historic blades and then added the same impurities to pure iron to make a blade that is indistinguishable from the historic blades.
So yes, he added the impurities (further thoughts on this - In historic times, perhaps the methods of completely purifying iron were not available. So the D blades were made using whatever kind of iron was available then. It seems that iron had certain impurities which gave D blade its character. Today, much better refining methods are available so iron is obtained without any impurities but to make a D blade, those trace impurities may be necessary)

We need to find an option that strengthens that these trace impurities are essential. That the blade maker could not have made the same type of blade without adding impurities.

B) The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.
Does that make it more likely that these trace impurities are necessary? No. Whatever source was used historically had trace impurities. The iron source used by the sword maker was unknown 2 centuries ago. Doesn't matter from where iron was obtained. He added the trace impurities and we need to say that it was essential to add those to get D blades.

D) Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted.
In old days, when blade makers ran out of iron from their original source, D blades stopped getting made. This means there was something special about the iron obtained from the original source. Now it becomes more likely that the trace impurities found in that source was the reason D blades could be made.
Hence, (D) is correct.
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For over two centuries, no one had been able to make Damascus bladesb [#permalink]
Hi AndrewN

I eliminated option D as it had no mention or any vague reference to "trace impurities". But having gone through the explanations, I understand that sometimes it is not necessary that the correct answer contains the exact key words. Option D opens up the possibility of creating an idea that there was indeed something special in the iron that was used to make the blades. We can therefore link this "special quality" of iron to trace impurities. Is my understanding correct?

Also what do you suggest I do to get better at such hard questions? I am having a tough time with such questions and even though a spend a considerable amount of time analyzing each answer choice, unfortunately I pick the wrong answer more often than not.
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Re: For over two centuries, no one had been able to make Damascus bladesb [#permalink]
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Namangupta1997 wrote:
Hi AndrewN

I eliminated option D as it had no mention or any vague reference to "trace impurities". But having gone through the explanations, I understand that sometimes it is not necessary that the correct answer contains the exact key words. Option D opens up the possibility of creating an idea that there was indeed something special in the iron that was used to make the blades. We can therefore link this "special quality" of iron to trace impurities. Is my understanding correct?

Also what do you suggest I do to get better at such hard questions? I am having a tough time with such questions and even though a spend a considerable amount of time analyzing each answer choice, unfortunately I pick the wrong answer more often than not.

Hello, Namangupta1997. Pardon the delay in my response; it was a busy day for me. Your read on answer choice (D) is accurate. To improve on more challenging CR questions in general, I would suggest you master Easy and Medium questions. The lines of reasoning that are brought to bear in those questions will show up in more challenging questions too. It is just that Hard questions do a better job of throwing reasonable-sounding options in front of us. And if you are blowing through 20 or more questions a day, stop. See what you can do with no more than 5. It is easy to fall into a mentality that practice makes perfect, that more is better, but that is not true if you keep making the same mistakes. You have to take the time to grasp the logical underpinnings of each question you practice, or your efforts will seem futile. Finally, see if you can study a question without getting the immediate gratification of knowing the answer. Reason your way to what you think is correct and just leave the question behind you, as you would on test day. Come back to it another day and see if you arrive at the same conclusion. When you grow accustomed to picking apart the questions and really spending some time with them, you start to gain insight.

Thank you for thinking to ask.

- Andrew
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Re: For over two centuries, no one had been able to make Damascus bladesb [#permalink]
KarishmaB wrote:
warrior1991 wrote:

B) The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.
Does that make it more likely that these trace impurities are necessary? No. Whatever source was used historically had trace impurities. The iron source used by the sword maker was unknown 2 centuries ago. Doesn't matter from where iron was obtained. He added the trace impurities and we need to say that it was essential to add those to get D blades.



hi experts, egmat, egmat

GMATNinjaTwo, VeritasKarishma, MartyTargetTestPrep, AndrewN,VeritasPrepBrian,GMATRockstar
KarishmaB

I am still confused by B.
after read through the whole topic, I realized I have not understood the argument correctly, but I am sure what I missed.

I have not gotten from where we can know the contemporary sword maker added the trace impurity, rather than he found the iron that itself includes the trace impurity. this misunderstanding makes me pick up B, which I thought if the source of iron is unknown 200 years ago, there is no source, so the abruption of making sword.

BTW, I just realized we can eliminate B because the source was not known 200 years ago, because the production is stopped during the 200 years, whether the source was unknown before 200 years ago is irrelevant to the duration of stop.

please clarify.
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Re: For over two centuries, no one had been able to make Damascus bladesb [#permalink]
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zoezhuyan wrote:
B) The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.

I am still confused by B.
after read through the whole topic, I realized I have not understood the argument correctly, but I am sure what I missed.

I have not gotten from where we can know the contemporary sword maker added the trace impurity, rather than he found the iron that itself includes the trace impurity. this misunderstanding makes me pick up B, which I thought if the source of iron is unknown 200 years ago, there is no source, so the abruption of making sword.

BTW, I just realized we can eliminate B because the source was not known 200 years ago, because the production is stopped during the 200 years, whether the source was unknown before 200 years ago is irrelevant to the duration of stop.

please clarify.


Hey zoezhuyan

Happy to help.

Yes, you are correct. Just because the modern source of the exact same type of iron was unknown 200 years ago, we cannot conclude that the makers of the Damascus blades ran out of their sources of the same iron 200 years ago. It is possible that those sword makers had plenty of supply of this specific type of iron. And it is equally possible that the reason why no one was able to make these blades for over two centuries was not that this specific type of iron was no longer available, but something else.

Answer choice D says that the production of Damascus blades by sword makers of the past ceased abruptly after those sword makers' original source of iron became exhausted. This strengthens our belief that that specific type of iron (with trace impurities) was essential for making Damascus blades. And this, in turn, strengthens the notion that the modern sword maker was able to recreate the Damascus blade by using the exact same type of iron (with trace impurities).

I hope this helps.

Happy Learning!

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Re: For over two centuries, no one had been able to make Damascus bladesb [#permalink]
Hi KarishmaB GMATNinja AjiteshArun
This question threw me for a loop!
Narrowing down to B and D was v easy, but i spent almost 20-30 mins arguing why (B) can't be the answer.
Finally i was able to eliminate (B), but i just wanted to run the logic by you to make sure that i have eliminated (B) for the right reasons:

Stimulus breakdown:

Conclusion: but a contemporary sword maker may just have rediscovered how

Premise: Using iron with trace impurities that precisely matched those present in the iron used in historic Damascus blades, this contemporary sword maker seems to have finally hit on an intricate process by which he can produce a blade indistinguishable from a true Damascus blade.

So, Because this Guy has matched the trace impurity---> he may have rediscovered the Damascus formula.

Argument assumes that ''Trace impurity'' are really really important.

If this were a weaken question, wouldn't we have destroyed the conclusion by saying that, Hey, you haven't considered several other bunch of stuff such as isotopic ratio or corrosive index?

Quote:
(B) The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.


This option utilizes the above logic a bit.
If new guy utilizes iron from a iron source which was unknown to old sword makers, then it is possible that their respective iron sources are similar in iron impurities but differs in 1000 ways.
It is possible that the new guy ignored several other important criteria, hence he may not be able to rediscover the Damascus formula.

Option (B)do not strengthen the idea that Trace impurity is essential rather puts a very small small dent on the hypothesis that trace impurities in the iron are essential for the production of Damascus.
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Re: For over two centuries, no one had been able to make Damascus bladesb [#permalink]
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ashutosh_73 wrote:
Hi KarishmaB GMATNinja AjiteshArun
This question threw me for a loop!
Narrowing down to B and D was v easy, but i spent almost 20-30 mins arguing why (B) can't be the answer.
...
Option (B)do not strengthen the idea that Trace impurity is essential rather puts a very small small dent on the hypothesis that trace impurities in the iron are essential for the production of Damascus.

Hi ashutosh_73,

You're thinking along the right lines. At best, option B doesn't help us show that trace impurities are essential for the production of Damascus blades. At worst, it (slightly) weakens the hypothesis.
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