In 1975 Chinese survey teams remeasured Mount Everest, the highest of

Question

In 1975 Chinese survey teams remeasured Mount Everest, the highest of the Himalayan mountains. Like the British in 1852, they used the age-old technique of “carrying in” sea level: surveyors marched inland from the coast for thousands of miles, stopping at increments of as little as a few feet to measure their elevation, and marking each increment with two poles. To measure the difference in elevation between poles, surveyors used an optical level—a telescope on a level base—placed halfway between the poles. They sighted each pole, reading off measurements that were then used to calculate the change in elevation over each increment. In sight of the peaks the used theodolites telescopes for measuring vertical and horizontal angles—to determine the elevation of the summit.

The Chinese, however, made efforts to correct for the errors that had plagued the British. One source of error is refraction, the bending of light beams as they pass through air layers of different temperature and pressure. Because light traveling. down from a summit passes through many such layers, a surveyor could sight a mirage rather than the peak itself. To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles of Everest’s summit, decreasing the amount of air that light passed through on its way to their theodolites. The Chinese also launched weather balloons near their theodolites to measure atmospheric temperature and pressure changes to better estimate refraction errors. Another hurdle is the peak’s shape. When surveyors sight the summit. there is a risk they might not all measure the same point. In 1975 the Chinese installed the first survey beacon on Everest, a red reflector visible through a theodolite for ten miles, as a reference point. One more source of error is the unevenness of sea level. The British assumed that carrying in sea level would extend an imaginary line from the shore along Earth’s curve to a point beneath the Himalaya. In reality, sea level varies according to the irregular interior of the planet. The Chinese used a gravity meter to correct for local deviations in sea level.   1 
Question 32.
 1. It can be inferred from the passage that refraction would be most likely to cause errors in measurements of a mountain’s elevation under which of the following conditions?

A. When there are local variations in sea level
B. When light passes through humid air
C. When theodolites are used relatively far from the mountain peak.
D. When weather balloons indicate low air temperature and pressure.
E. When sea level has been carried in to Within five to twelve miles of the summit.

2 
 2. Which of the following best describes the purpose of the sentence in lines 23-25 (“The Chinese , however,...the British”)?

A. Introduce a definition
B. Signal a transition in focus
C. Summarize the preceding paragraph
D. Draw a contrast between two different theories.
E. Present information that contradicts the Preceding paragraph.

3 
 3. Which of the following is NOT mentioned as a possible source of error in surveying mountain elevation?

A. Mirages
B. Refraction
C. Inaccurate instruments
D. Variations in sea level
E. Uncertainty about the exact point to be Measured

4 
Question 35
 4. The primary purpose of the passage is to

A. provide details about improvements to a process
B. challenge the assumptions underlying a new method
C. criticize the way in which a failed project was carried out
D. call for new methods to solve an existing problem
E. explain the theory behind a new technique

5 
 5. The passage suggests which of the following about the technique used by the Chinese in their measurement of Mount Everest?

A. The Chinese employed the same assumptions about sea level as the British but used more accurate methods.
B. The Chinese used a different instrument for measuring the difference in elevation between increments than the British had.
C. The Chinese used the same basic technique as the British, supplementing it with modern refinements to knowledge and methods.
D. Since the accuracy of the technique of carrying in sea level had been challenged, the Chinese were obliged to develop a new technique to replace it.
E. Since few advances had been made in the field of mountain surveying, the Chinese used no equipment in addition to what the British had used.

crick20002002 · Accepted Answer

I also got CBCA.

For the first question, Since its an inference question, the passage must contain proof sentences for the inference.

To reduce refraction errors, the Chinese team carried in sea level to
within five to twelve miles of Everest’s summit, decreasing the amount of air
that light passed through on its way to their theodolites 
 
The above effectively means that the refraction error is closely related to distance of theodolite from the peak.==> C

D cannot be the answer, definition of refraction mentions bending of light due to difference in pressure and temperature and not absolute low pressure and low temperature.

Crick

GMATNinja · Answer

This one doesn't seem to actually come from an official source, so I wouldn't worry about it too much. It was originally tagged as coming from the GMAC Paper Tests, but I just searched all of the publicly available exams, and it isn't in there. I changed the source to "other" -- if someone does find the source of this passage, please take a screenshot and post it!

Until then, please don't waste too much of your precious study time worrying about it.

Skywalker18 · Answer

Took around 8 mins 20 seconds , including 4 mins to read . Got the first question incorrect . In my opinion, OA D seems contentious .

Q32. It can be inferred from the passage that refraction would be most likely to cause errors in measurements of a mountain’s elevation under which of the following conditions?

One source of error is refraction,  the bending of light beams as they pass through air layers of different temperature and pressure . Because light traveling. down from a summit passes through many such layers, a surveyor could sight a mirage rather than the peak itself. To reduce refraction errors,  the Chinese team carried in sea level to within five to twelve miles of Everest’s summit, decreasing the amount of air that light passed through on its way to their theodolites.  The Chinese also launched weather balloons near their theodolites to measure atmospheric temperature and pressure changes to better estimate refraction errors.

A. When there are local variations in sea level -- Incorrect
B. When light passes through humid air -- Irrelevant -- the cause of refraction is passage of light through air layers of different temperature and pressure
C. When theodolites are used relatively far from the mountain peak. -- greater distance itself won't cause refraction, but with increasing distance the probability of light passing through air layers of different temperature and pressure
D. When weather balloons indicate low air temperature and pressure. -- here we have to assume that a few layers of air through which the light passes will have air temperature and pressure that is not low -- maybe normal or high ?
E. When sea level has been carried in to Within five to twelve miles of the summit. -- This was a way to reduce refraction errors that was adopted by Chinese

AjiteshArun  ,  mikemcgarry  , daagh  , egmat  ,  GMATNinja  ,  sayantanc2k  ,  RonPurewal  , ChiranjeevSingh  other experts -- can you please help with Q32 ?

MagooshExpert · Answer

Hi Skywalker18 ! I'll jump in for Mike here

In my opinion, this is not a very well written question, and not up to GMAT standards. As you and others have pointed out, both C and D have elements that could be considered correct. I think your analysis is correct here - for choice C, with increasing distance, there is a higher probability that light will have to pass through regions of different temperature and pressure, causing refraction. This is supported by the part of the passage that states "To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles of Everest’s summit, decreasing the amount of air that light passed through on its way to their theodolites." For choice D, we can assume that if there is low temperature and pressure closer to the summit, there are likely different layers of temperature and pressure that the light has to travel through, which also will cause refraction errors. So both answer choices have some merit here; again, I don't think this is a very well-written question. I wouldn't say that either C or D is substantially more supported by the passage. Hope that's helpful!

-Carolyn

ballest127 · Answer

Hi expert,

I would like to ask for OE for Q1.

Thank you.

achanak · Answer

Hi  GMATNinja 
Attached screenshot referenced. The source of the passage is the official practice exam(s). Though it appears the contentious question (Q1 above) has been removed.

GMATNinja · Answer

Thanks for tracking that down! We'll continue to ignore the first question until it's verified, but will assume that the rest are legit

.

GMATyodasimran · Answer

Hey experts

KarishmaB   GMATNinja   AjiteshArun   DmitryFarber   ExpertsGlobal5   mikemcgarry   sayantanc2k

Could you please help me with Q35 - primary purpose of passage. I am confused between options A and E.

Paragraph summary -
paragraph 1 - Details about how measurement was done in 1852 by Britishers
paragraph 2 - Limitations in the technique of Britishers and how was it rectified by Chinese

1. Option A - provide details about improvements to a process(This is only discussed in paragraph2)
2. Option E - explain the theory behind a new technique(This is only discussed in paragraph 1)

How to select one out of them? Am i missing anything?

KarishmaB · Answer

(E) is incorrect because Chinese did not use a new method. They used the technique of carrying in sea level just as the Britishers did.

"Like the British in 1852, they used the age-old technique of “carrying in” sea level: surveyors marched inland from the coast for thousands of miles, stopping at increments of as little as a few feet to measure their elevation, and marking each increment with two poles."

Para 2 discusses how they the Chinese corrected the errors that had plagued the Britishers. So option (A) is correct.

In 1975 Chinese survey teams remeasured Mount Everest, the highest of

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In 1975 Chinese survey teams remeasured Mount Everest, the highest of

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