GMATPREP CR: Driving the steep road to the mountaintop Inca

[Khush]

Hi Ron,
I solved the below GMATPrep software weaken problem following your method (as shown in your Thursdays session), but chose a wrong answer.
Please correct me where am I wrong.

Driving the steep road to the mountaintop Inca ruins of Machu Picchu is potentially dangerous and hiking there is difficult. Now the Peruvian government is installing a cable car that will make access much easier, and hence result in a large increase in tourism. However, since the presence of large numbers of tourists tends to accelerate the deterioration of a site, installation of the cable car is certain to result in harm to the ruins.

Which of the following, if true, most seriously calls into question the argument?

A. The daily number of tourists that are expected to take the cable car to Machu Piccu is smaller than the original resident population of Incas.
B. The construction of the cable car terminal at Machu Picchu will require the use of potentially damaging heavy machinery at the site.
C. Machu Picchu is already one of the most popular tourist sites in Peru.
D. Natural weathering will continue to be a more significant cause of the deterioration of Machu Picchu than tourist traffic.
E. The cable car will replace the tour buses whose large wheels and corrosive exhaust at present do significant damage to the site.

Premise1: Driving up is dangerous and hiking is difficult
Premise2: cable car will solve the above issue and will also result in an increase in tourism.
Premise3: The increase in the number of tourists will accelerate the damage to a site
Conclusion: Installation of the cable car will surely result in harm to the ruins of Machu Picchu
Identify the Issue: Will installation of the cable car result in harm to the ruins?
Identify the issue explicitly: Will installation of the cable car result in an "increase in tourism", which in turn will cause harm to the ruins of Machu Picchu?

I chose choice D, as it says some reason superior to the
"Increase in number of tourists "reason.
I also had a doubt in choice E, which is the right answer here. However, I could not justify how an advantage of "Cable cars" over the "tour buses" is a weakener.
"Increase in the number of tourists" due to the cable car facility causes the harm. Isn't it? Why an advantage of the cable car is shown as a weakener?

I can feel i have some reasoning issue here.But i am unable to find out where. Please help here.

[RonPurewal]

Identify the Issue: Will installation of the cable car result in harm to the ruins?

^^ This is the issue.

Identify the issue explicitly: Will installation of the cable car result in an "increase in tourism", which in turn will cause harm to the ruins of Machu Picchu?

^^ Nope. The passage states that the cable car WILL result in an increase in tourism; this is stated as a fact that's not at all in doubt.

You just have to find something that attacks the idea that extra harm will be done to the ruins.

The stuff in the argument is pretty much airtight. The cable car WILL bring more tourists, and a greater number of tourists DOES accelerate weathering. So, you're not going to be able to attack those things.
The only possibility that's left is -- what is the cable car replacing? If the cable car is replacing something that is currently causing a great deal of damage, then the argument isn't sound anymore, because one would have to consider the cable-car damage relative to the damage caused by whatever is currently there.

[RonPurewal]

Choice D says that natural forces already cause harm to the ruins, but that doesn't have any effect on a discussion of the cable car. (The cable car can still cause damage over and above what's caused by nature.)

[RonPurewal]

Analogy:
Fruit contains the sugar fructose, which is quickly metabolized into fat if not burned immediately by exercise. Therefore, people who eat fruit will be fatter than people who don't.
(Here, sugars play the same role as tourists. Obesity plays the same role as weathering of rock.)

Choice D is like saying "Lack of exercise is a greater cause of obesity than sugar consumption." Not the point, because we're only concerned with the effect of sugar consumption. Even if people are getting fatter as a baseline because they aren't exercising, we're only concerned with the additional (marginal) effect of the sugar.

Choice E is like saying "When people eat fruit, they normally eat it as a substitute for other sweet snacks that are also high in fructose."
You see how that works, right? So eating fruit = taking away the other sweet snacks = maybe not so bad after all. Same deal with cable car = take away the tour buses.

[Khush]

WOW!!

Thanks a ton for the awesome explanation , Ron !!!

Till today i was wrongly considering the facts as part of the ISSUE in the argument.

Things are 100% clear now...

I will never forget the analogy presented by you...

I feel you can read a student's mind..

Please take a bow.....

[RonPurewal]

I will never forget the analogy presented by you...

If you have trouble with a CR problem, try to make an analogy for it.
Remember, the logic isn't the hard part. The hard part is trying to think intuitively about things like weathering of ancient rocks -- i.e., things that most normal people don't really consider in their daily lives.
If you can successfully make an analogy, then you can get rid of that factor of the challenge. (You may need a decent amount of time to come up with an analogy, especially at first.)

I feel you can read a student's mind..

Nah. You're giving me way too much credit here -- I'm just explaining how the problem objectively works. (It's not hard to read minds when there's only one thing those minds are supposed to be thinking!)

[Khush]

You are right Ron.
I do try my best to create analogies , but find it difficult in most of the cases. Hope it will come naturally with practice.

You are being humble here. You do deserve the credit for the explicit and unique explanations you always provide.

In fact i have never seen any questions left unattended in this forum.

Much appreciate the help!!

Thanks.

[RonPurewal]

You are right Ron.
I do try my best to create analogies , but find it difficult in most of the cases. Hope it will come naturally with practice.

You are being humble here. You do deserve the credit for the explicit and unique explanations you always provide.

Well, thanks.

In fact i have never seen any questions left unattended in this forum.

If the volume of posts surpasses what we can reasonably handle, then we'll start to prioritize posts from paying clients (= posters who have purchased our courses and/or materials). If that happens, then some posts from free users will remain unanswered.
That typically happens during the fall season (especially close to round 2 admissions deadlines), but it didn't happen this year. Less forum traffic than usual.

[FanPurewal]

OMG!
i have searched for thousands times on the internet to find an convincible explanation of choice E...

WHY didn't i discover Ron' explanation earlier? :(

thanks for 9876336778999 times is not enough!

and by the way, if i edit the last sentence (conclusion) like this:
installation of the cable car is certain to result in harm to the ruins-->installation of the cable car is the only reason of deterioration of the site

will D be the appropriate answer?



thanks thanks ....

[RonPurewal]

You can't write a choice like that. It directly contradicts the passage, which states that the presence of large numbers of tourists is something that can cause physical deterioration.

Facts stated in the passage are not lies.

[VikrantS137]

C says - Machu Picchu is already one of the most popular tourist sites in Peru.

Hence, # of tourists now = 400,000 (assume)
After installing the cable car increase in # of tourists = 80,000 (large #)

Hence total # of tourists after installing the cable car = 480,000

400,000 tourists v/s 480,000 tourists - not much of change in the deterioration.

Why C is wrong?

[RonPurewal]

in the passage, it is stated, as a FACT, that the cable-car project will bring "a large increase in tourism".
the point is to interpret these sorts of things according to common sense.
if something can be described as a "large increase", then it must be "large" relative to the original value.

here, you have chosen numbers that represent a SMALL increase (only twenty per cent), thus contradicting the given facts.

[RonPurewal]

also, more importantly, DO NOT 'PLUG IN NUMBERS' ON CR PROBLEMS.

'plugging in numbers' cannot possibly add any value—and, all too often, you'll 'plug in' numbers that belie the facts actually stated in the argument.

we've already gone over this a couple of times recently:

here...
https://www.manhattanprep.com/gmat/foru ... ml#p117603

and here...
https://www.manhattanprep.com/gmat/foru ... ml#p117601

as you can see, this 'technique' is not getting you anywhere. really, don't do it.