Veritas Prep Daily GMAT Challenge – Reading Comprehension and Data Sufficiency!

by on June 30th, 2010

Each day this week, we will be challenging the Beat The GMAT community with a Verbal and Quant question that we consider especially difficult. The first 10 people to provide the correct answer to either question in the comments section will win a Veritas Prep GMAT prep book.  Make sure to submit your answer(s) by 5pm PDT today to be eligible for the contest.  Winners will be announced in tomorrow’s Veritas Prep post.  Good luck!

Reading Comprehension Challenge Question

While popular science tends to favor extragalactic astronomical research that emphasizes current challenges to physics, such as the existence of dark matter, dark energy, and Cosmic inflation, significant research continues to take place in the field of planetary astronomy on the formation of our own solar system.  In early attempts to explain this phenomenon, astronomers believed in the encounter, or “rogue star,” hypothesis, which suggests that matter was tidally stripped away from our sun as a larger star passed within a gravitationally-significant distance some billions of years ago.

The encounter hypothesis postulates that after being stripped away, the matter cooled as it spun farther from the sun, and formed planets with their own centers of gravity.  This hypothesis conveniently accounts for the fact that all planets in the solar system revolve in the same direction around the sun; it is also consistent with the denser planets remaining closer to the sun, and the more gaseous planets traveling further away.

The encounter hypothesis explained the phenomenon sufficiently enough that it allowed scientists to focus on more immediately rewarding topics in physics and astronomy for most of the first half of the 20th century.  Closer investigation, however, found several significant problems with the encounter hypothesis, most notably that the hot gas pulled from the sun would not condense to form dense planets, but rather would expand in the absence of a central, gravitational force.  Furthermore, the statistical unlikelihood of a star passing in the (astronomically speaking) short time of the sun’s existence required scientists to abandon the encounter hypothesis in search of a new explanation.  Soon after, astronomers formed a second theory, the nebular hypothesis, which submits that the solar system began as a large cloud of gas containing the matter that would form the sun and its orbiting planets.  The nebular hypothesis suggests that when the cloud reached a critical mass, it collapsed under its own gravity. The resulting angular momentum would have morphed the nebula into a protoplanetary disc, with a dense center that generated intense heat and pressure, and a cooler, thinner mass that revolved around it.  The central mass would have continued to build in density and heat, forming the sun, while the centrifugal force around the disc’s edge kept smaller masses from being pulled in to the sun; those masses, upon cooling, would break off to become planets held in orbit by the competing gravitational force of the sun and centrifugal force of their orbital inertia.

The nebular hypothesis, however well it explained the sun’s formation, remained problematic in its ability to account for the formation of several planets with differing physical and chemical properties.  Encouraged by their advance toward a provable hypothesis for the solar system, scientists have recently come to adopt a third hypothesis, the protoplanet hypothesis.  This currently accepted theory holds that the gaseous cloud that would form the solar system was composed of particles so cold that even the heat of the forming sun could not significantly impact the temperature of the outer reaches of the cloud.  Gas in the inner region, within what scientists refer to as the frost line, was quickly either burned or dispersed, leaving a small amount of metallic matter, such as nickel and iron, to form the inner planets.  Such matter would need to have an extremely high melting point to avoid becoming liquefied, ensuring that Mercury, Venus, Earth, and Mars would remain small and dense.  Outside the frost line, however, gas was kept cool enough to remain in solid, icy states.  Over time, planets such as Jupiter and Saturn would amass large quantities of frozen gas, enough to grow to hundreds of times the size of the Earth.

According to the nebular hypothesis, a protoplanetary disc formed in the early stages of the solar system because

(A) Cold gases in the outer reaches of the nebula were repelled from the hot center of the spiraling mass.
(B) Gravity forced the nebular cloud to contract upon itself, creating significant angular momentum.
(C) Cooling matter held safely from the center of the mass could eventually form planets.
(D) Matter with a high melting point could not be consumed by the heat in the center of the disc.
(E) Gravity from a passing star pulled matter away from the sun, allowing planets to form around it.

Data Sufficiency Challenge Question

Is  x <= 0?

(1) x^2 = 9x
(2) delim{|}{x}{|} = -x

(A) Statement (1) ALONE is sufficient, but statement (2) ALONE is not sufficient.
(B) Statement (2) ALONE is sufficient, but statement (1) ALONE is not sufficient.
(C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
(D) EACH statement ALONE is sufficient.
(E) Statements (1) and (2) TOGETHER are not sufficient.

Solutions from Yesterday’s Challenge Problems

Geometry Challenge Problem Solution

Read the problem first.

When tackling Geometry problems, such as this one that appears in the Veritas Prep Advanced Word Problems & Quantitative Review lesson, it is important to note that the GMAT tests a finite number of geometric concepts – but also that you’re well-served to consider all of the possible concepts that could relate to a problem.  GMAT geometry is a lot like an episode of MacGyver – with very few tools, you should be able to find a way to solve a complex problem, and in the most difficult of problems you may have to employ tools that don’t seem at first to be relevant.

Here, we can use Pythagorean Theorem (or its offshoot 3-4-5 side ratio) to determine that the side QS has a length of 5.  From there, however, the Pythagorean calculations get messy.  With right triangles, it’s also quite easy to determine the area, as right triangles have a built in base-height perpendicularity.  Here, we can use 4 as the base and 3 as the height, to find that the area is:

½ (4)(3) = 6

Because the area has to be the same regardless of which base-height combination is used, we can see that, if side QS were used as the base, then the line PR – for which we are solving – would be the height.  Knowing that the area is 6 and that line QS is 5, we can use the area formula to solve for the height, line PR:

A = ½ bh

6 = ½ (5)h

12 = 5h

12/5 = h

Therefore, line PR has a length of 12/5, and B is the correct answer.

When approaching geometry problems in particular, but GMAT questions in general, keep in mind that the questions are small enough in scope that it almost never hurts to solve for “the next unknown” and fill in more pieces of the puzzle.  If the calculations become overly involved or time-consuming, you may want to reconsider (or use other strategies such as number properties or backsolving techniques), but overall you’re unlikely to find that the GMAT will ever lead you on a wild-goose-chase solving for unnecessary variables; you should be able to use just about every variable for which you can solve to track down your answer.

Here, simply by taking inventory of everything you knew about the triangle – sides, perimeter, area – you were able to find a simple way to solve the problem without resorting to ugly quadratic algebra.  With other problems, continue to take inventory of what you know and for what you can quickly solve; adding more tools to your toolkit on any problem should allow you to get in touch with your inner MacGyver and save the day in ingenious fashion.

Congratulations to the following people for correctly answering the question:

Vibhavender Y, Amit, Ajpshergill, Pardeep, Ank, Govardhan, Neil Zieses, Nicole, Vinodh Ramadoss, and Kissthegmat!  We will be sending you a message shortly requesting information about where to send your book.

Sentence Correction Challenge Problem Solution

Read the problem first.

In the Veritas Prep Sentence Correction lessons, you’ll learn that it’s critical to look for specific errors when viewing Sentence Correction problems.  The VAMPIRES checklist, covered in the Sentence Correction 1 book, gives you an outline of the errors for which to search, saving time and improving accuracy.

This question contains a classic Modifier error.  Modifiers are descriptive phrases, and errors occur when they do not modify what they are supposed to.  The initial sentence contains two modifiers:

“Unlike water” and “Which is complimentary”

The rule for reflexive pronouns (which, who, etc.) is that they must describe the word directly next to them.  Here, “which” describes water, so no error is present.  Because the modifier is correct, you can mentally eliminate it from the remainder of your read, as modifiers separated by commas provide extra information that is nonessential to the rest of the sentence. (There is more to this “Slash and Burn” Sentence Correction strategy for making sentences shorter and easier to process; it is detailed in the Sentence Correction 1 book.)

With that out of the way, the rest of the sentence reads “Unlike water, all passengers…”  This is a modifier error – passengers would never be like water, as the two items are completely different and not an apt comparison.  Accordingly, choice A is incorrect.

A quick glance at the other sentences shows that none of the sentences contains a proper modifier – each attempts to describe “passengers” with “water”.

However, a closer look at choice C shows that it is not a modifier at all; because it has its own subject and verb – “unless the drink is water” – it is a separate clause, and therefore correct.  Because it’s not a modifier, it isn’t beholden to the modifier rules, and is grammatically correct.  C is the correct answer.

On questions such as this, you may experience a tendency to look at other decision points – this one gives you the opportunity to debate “unlike” vs. “besides”; “complimentary” vs. “free of charge”; and other idiomatic or preference-based decisions.  However, because there are so many variations of idiomatic expressions – the English language is incredibly intricate, and certain idioms are debated region-to-region making it even harder – you’re much more likely to run into unclear decisions or to mis-memorize idioms and choose incorrectly as a result.  If you focus on the major error categories, you’ll just about always (some, but fewer than people think, idioms are explicitly testable and covered in the Sentence Correction 2 lesson) find your decision to be much easier and much more logical.   In finding the most efficient way to make a decision, you’ll also demonstrate an important business skill; after all, the GMAT has a method to its question-writing madness!

Congratulations to the following people for correctly answering the question:

Vibhavender Y, Amit,  Pardeep, Ank, Govardhan, Neil Zieses, Nicole, Vinodh Ramadoss, Kissthegmat and Vivek!  We will be sending you a message shortly requesting information about where to send your book.

Free Trial Class This Thursday: Join Brian Galvin, Veritas Prep’s Director of Academic Programs and one of our highest-rated GMAT instructors, this Thursday July 1 for a 3-hour Combinatorics & Probability GMAT lesson.  This is lesson 12 of Veritas Prep’s 14 lesson Complete Course! RSVP TODAY.

This week only – 50% off Veritas Prep GMAT books: Just for this week, take 50% off Veritas Prep GMAT books. Use discount code VPBooks10.

49 comments

  • For the DS question, the answer is (D)

    • oops.. realised the folly of my ways :)

      DS:B

  • Data Suff : B

    • RC - B

  • Reading comprehesion : B
    DS: B

    • RC: answer B can be found in these lines.."The nebular hypothesis suggests that when the cloud reached a critical mass, it collapsed under its own gravity. The resulting angular momentum would have morphed the nebula into a protoplanetary disc,"
      DS: 1) x sqrd = 9x ==>x can be 9 or zero eliminate A,D
      2)mod x = -x implies x< 0 ..suff...answer B

  • Data Sufficiency: B

    • Reading Comprehension: B

  • Math - B
    the first condition looks like it can be simplified to x=9, but this leaves out the case where x=0, which is also valid. Since x can equal 0, this makes this first statement insufficient to determine if x<=0.

    The second statement can be simplified to x<=0 because only these numbers when multiplied by -1 will yield the same value as |x|.

    Since (1) is I and (2) is S, the answer is B

    • Reading - B

  • datasufficiency B

  • Reading comp : B
    Data Suff : B

  • RC: B
    DS: B

    • Hi Sarathy,

      Congratulations again on correctly answering multiple Daily Challenge Questions. Please send me a PM (VP_Marisa) with your shipping address and phone number so we can ship you your books.

      Thank you,
      Marisa

  • DS: B

    (1) is insufficient b/c x can be either 0 or 9.
    (2) is sufficient b/c x must be 0 or negative.

    • Hi Nicole,

      Congratulations for correctly answering the Data Sufficiency, Geometry, and Sentence Correction Challenge Problems. Please send me a PM (VP_Marisa) with your shipping address and phone number. I'd like to ship you your books as soon as possible.

      Thank you,
      Marisa Peck

  • RC:B
    DS:B

  • rc -b
    ds -b

    • Hi Pavan,

      Congratulations on correctly answering multiple Veritas Prep Daily GMAT Challenges! Please send me a PM (VP_Marisa) with your shipping address and phone number so I can have the books sent to you.

      Thank you,
      Marisa Peck

  • DS - B
    RC - B

  • rc B

  • RC: B
    DS: B
    A) x2 = 9x
    x (x-9) = 0
    x = 0 or x = 9 Insufficient

    B) |x| = -x
    It's possible only when x is negative e.g. x = -5
    |-5| = 5 = -(-5) = 5

  • RC: B

    Because the text states: "The nebular hypothesis suggests that when the cloud reached a critical mass, it collapsed under its own gravity. The resulting angular momentum would have morphed the nebula into a protoplanetary disc"

  • B & B

  • RC: B
    First read the question and found that it is a specific question type, so no need to read the complete passage.

    Keywords here are "nebular hypothesis" and "protoplanetary disc". They both are appearing together for the first time in the middle of 2nd paragraph, and this is the place where lies the answer.

    After reading this sentence and going thru the answer choices, only option B is in scope and hence is the best answer.

    DS : B

    Statement 1:

    x^2 - 9x = 0
    => x=0, 9

    Hence Statement 1 is INSUFFICIENT.

    Statement 2:
    |x| = -x
    => x is negative

    taking examples, if x 2 = 2, correct

    if x>0, say 2
    |2| = -(2)
    2 = -2, incorrect

    Statement 2 in itself is SUFFICIENT

    and hence the correct answer is B.

  • My an swers are
    Ds : b
    RC : B

  • RC : C
    DS : B

    Reading Comprehension :

    Cooling matter is future planets held safely by centrifugal force.

    (C) Cooling matter held safely from the center of the mass could eventually form planets.

    The nebular hypothesis suggests that when the cloud reached a critical mass, it collapsed under its own gravity. The resulting angular momentum would have morphed the nebula into a protoplanetary disc, with a dense center that generated intense heat and pressure, and a cooler, thinner mass that revolved around it. The central mass would have continued to build in density and heat, forming the sun, while the centrifugal force around the disc’s edge kept smaller masses from being pulled in to the sun; those masses, upon cooling, would break off to become planets held in orbit by the competing gravitational force of the sun and centrifugal force of their orbital inertia.

    B - doesn't explain the smaller masses future planets
    being kept from being pulled to the center.

    Data sufficiency

    (2) alone sufficient :
    By definition : abs(x) = x for x>=0 and abs(x) = -x for x<=0
    abs(x)=-x x<=0

    x(x-9)=0 x=0,9 not sufficient

    • The question asks the reason for planetory discs formation:
      this answers it: "The nebular hypothesis suggests that when the cloud reached a critical mass, it collapsed under its own gravity. The resulting angular momentum would have morphed the nebula into a protoplanetary disc"

    • Thanks Vijay - you are probably right.
      Noticed that I didn't read the question carefully.

      RC - B
      DS - B

  • Verbal: B
    Maths: D

  • RC: B
    DS: B

  • DS: the answer is B.
    Statement 1: we can rearrange the equation as x^2-9x=0. therefore, x=9 OR x=0. --> insufficient.

    Statement 2: by the rules of absolute value sign, it is sufficient.

  • RC- B
    DS- C

  • RC: B
    DS: B

  • RC Q
    answer : B
    second para has the answer

    DS
    B

    i) x can be 0 or 9
    x=0 satisfies the equation but x=9 does not
    insuff

    ii) suff

  • RC - B
    DS - B

  • Data Sufficiency... Answer B

    from statement 1 --
    x^2 = 9x
    or
    x^2-9x = 0
    or
    x(x-9) = 0 so either x = 0 or x = 9 (Insufficient)

    from statement 2

    |x| = -x can be true only for negative values of x and hence sufficient and hence the answer.

    • RC

      Answer - Choice B

    • |x| = -x can be true only for negative values of x and zero.

  • RC:

    Answer - choice B

  • RC - B
    "The resulting angular momentum would have morphed the nebula into a protoplanetary disc, with a dense center that generated intense heat and pressure, and a cooler, thinner mass that revolved around it. "

    DS - B

    St. 1 : x = 0, 3, 0r -3 --> Insufficient
    St. 2 : for |x| + x = 0, x < 0 or x = 0

  • Reading Comprehension:B
    Data Sufficiency:B

  • For the DS question answer is D

  • RC: C
    "with a dense center that generated intense heat and pressure, and a cooler, thinner mass that revolved around it."
    DS: C
    1st statement is not sufficient as both 0 and 9 satisfy the condition.
    2nd statement is also insufficient as |0| = -0 is not true. 0 is neither negative nor positive.
    Together they are sufficient, as both 9 and 0 (from 1st statement) do not satisfy the Main statement (x <= 0 ?)

  • RC : B

    DS : D

  • RC - B
    DS - D

    • RC - B
      DS - C
      Expl -

      From (1) x = -+3
      From (2) x = -ve.

      So we need both (1) and (2).

  • People who answered B on the Ds Q, what says that x can't be 0 in st(2) ?

  • hey can we get comprehenshion books free online

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