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GMAT 800


Flawed Thinking in GMAT Critical Reasoning
Critical Reasoning is a skill that you cannot develop in a couple of days. But GMAT Critical reasoning can be mastered if you understand some of the common pitfalls in our logical deduction. The most common mistakes are made in Syllogism.



What is Syllogism?


A Syllogism is a type of argument where you have a conclusion based on one or more premises. Let’s look at an example

Premise 1: All roses are flowers

Premise 2: Some flowers have thorn

Conclusion: Therefore Some roses have thorn


Most GMAT test taker would agree with the conclusion or naturally make such conclusions when they are presented with similar critical reasoning questions. The CONCLUSION is wrong! We are intuitive creatures. Even when our logical mind asks us to think before making any conclusion, the lazy intuitive mind will force us to make the obvious wrong conclusion. Another factor that contributes to the wrong conclusion is the use of our knowledge about roses (that it has thorns) to make the conclusion.

Remember, GMAT Critical reasoning requires you to...


Set A consists of integers -9, 8, 3, 10, and J; Set B consists of integers -2, 5, 0, 7, -6, and T. If R is the median of Set A and W is the mode of set B, and R^W is a factor of 34, what is the value of T if J is negative?

(A) -2
(B) 0
(C) 1
(D) 2
(E) 5

Solution

This problem demonstrates a helpful note about statistics problems – quite often the key to solving a stats problem is something other than stats: number properties, divisibility, algebra, etc. The statistics nature of these problems is often just a way to make a simpler problem look more difficult.

Here, the phrase “factor of 34? should stand out to you, as there are only four factors of 34, so you can narrow down the possibilities pretty quickly to 1, 2, 17, and 34. And because the number in question must be an exponential term that becomes a factor of 34, it’s even more limited: 2, 17, and 34 can only be created by one integer exponent – “itself” to the first power.

The base of that exponent is going to be the median of Set A, and because we know that the median of Set A will be 3 (a negative term for variable J means that 3 will be the middle term), the question becomes that much clearer. 3^W can only be a factor of 34 if it’s set equal to 1, and the only way to do that is for W to be 0. REMEMBER: anything to the power of...


A newborn kangaroo, or joey, is born after a short gestation period of only 39 days. At this stage, the joey’s hind limbs are not well developed, but its forelimbs are well developed, so that it can can climb from the cloaca into its mother’s pouch for further development. The recent discovery that ancient marsupial lions were also born with only their forelimbs developed supports the hypothesis that newborn marsupial lions must also have needed to climb into their mothers’ pouches.

The argument in this passage relies on which of the following assumptions?

[A] All animals that are born after a short gestation period are born with some parts of their bodies underdeveloped.
[B] Well developed forelimbs would have been more advantageous to ancient marsupial lions than well developed hind limbs would have been.
[C] If the newborn marsupial lion did not climb into its mother’s pouch, then paleontologists would be able to find evidence of this fact.
[D] Newborn marsupial lions that crawled into their mothers’ pouches could not have done so had they not had only their forelimbs developed at birth.
[E] Newborn marsupial lions would not have had only their forelimbs developed if this development were of no use to the marsupial lions.


...


In the Business program at a university, all candidates for the MBA in International Business who entered the program after 1990 took a seminar on Microeconomics, and all candidates for the MBA in International Business who entered the program after 1994 took a seminar on Applied Economics.

If a student in the Business program described above took a seminar on Microeconomics but did not take a seminar on Applied Economics, which of the following must be true?

(A) The student entered the Business program prior to 1995.
(B) The student entered the Business program after 1990 and prior to 1995.
(C) If the student was a candidate for the MBA in International Business, then the student entered the program prior to 1994.
(D) If the student was a candidate for the MBA in International Business, then the student entered the program prior to 1991.
(E)If the student was a candidate for the MBA in International Business, then the student entered the program after 1990 and prior to 1995.

Solution:

(A): This option does not mention whether the student is an MBA candidate or...


Market research has shown that the newest model of E-Phone gained widespread popularity not due to technical superiority but through seamless and intuitive design.

A. gained widespread popularity not due to technical superiority but through seamless
B. gained widespread popularity not only due to technical superiority but also through seamless
C. did not gain widespread popularity due to technical superiority but through seamless
D. did not gain widespread popularity in consideration of technical superiority but rather due to seamless
E. gaining widespread popularity not due to technical superiority but also through seamless


Explanation:  
In the construction "not...but", the words following "not" and "but" should be in parallel form. In this case, "not" and "but" are parallel because they are both followed by a phrase.

a.Choice A is the correct answer. "Not" and "but" are each followed by a phrase, and so are parallel. Also, "gained" is the correct past tense construction for the concept.
b.Choice B is not the correct answer. This changes the meaning of the sentence.
c.Choice C is not the correct answer. The verb "gain" follows "not", but a phrase follows "but," so the construction is not parallel.
d.Choice D is not the correct...


             Natural selection, the central doctrine of
             Darwinism, has been explained as the "survival of the
             fittest." On this process has depended the progress
             observable throughout organic nature to which the term
(5)         evolution is applied; although there has been from time
             to time degradation, this has had relation only to
             particular forms, organic life as a whole evidencing
             progress towards perfection. When man appeared as the
             culmination of evolution under terrestrial conditions,
(10)       natural selection would seem almost to have finished its
             work, which was taken up, however, by man himself, who
     ...


A leading board member of AutoSnip Co., makers of an automated home haircutting system, recently stated that the company was in terrible shape and headed for a disastrous year. His concern was that, since the introduction of the AutoSnip III last year, calls to the customer service line have nearly doubled, indicating that people are very unhappy with the new product. Although it's true that it is the job of responsible board members to raise issues of concern, in this case the board member's analysis of the situation is mistaken. The customer service line handles not only complaints but also sales, and the majority of the new calls have been to place new orders.

What role do the two boldfaced selections play in the above argument?

A.The first provides evidence supporting the main conclusion of the argument; the second provides evidence supporting a conclusion that the argument opposes.
B. The first provides evidence, an interpretation of which supports the main conclusion of the argument; the second provides evidence supporting the main conclusion of the argument.
C. The first provides incontrovertible evidence opposing the main conclusion of the argument; the second provides evidence supporting the main conclusion of the...


The function g(x) is defined for integers x such that if x is even, g(x) = x/2 and if x is odd, g(x) = x + 5.  Given that g(g(g(g(g(x))))) = 19, how many possible values for x would satisfy this equation?

A. 1
B. 5
C. 7
D. 8
E. 11

Explanation:

The easiest way to approach this problem is probably to work backwards, at least until we see a pattern.

With g(...) = 19, then we can consider which operation applied to (...).  If it was x/2, then (...)= 38.  38 is even so that is fair.   If it was x + 5, then (...) was 14.  14 is even, so that operation would not have been applied.

On paper, you could make a tree, with 19 as the root, and 38 as the first node.  

Next consider 38.  38 could have come from 76/2 or 33 + 5.  Two possibilities give us two nodes branching from 38:

19  -> 38 -> 76, 33.

We can now observe the pattern that with an odd number, it must have come from an even, but an even could come from either of two numbers.

Therefore our 76 will branch into 2 numbers, and the 33 into just one.

33 -> 66
76 -> 73, 152..

We can represent this as shown here:

...


Grockit Questions

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 to answer the question asked, and additional data are needed.



Explanation:
This question asks whether the information in one or both statements is sufficient to find a specific value. But we don't actually have to determine the value, just know that it can be determined.

(1) Quadratic equations have two solutions. However, sometimes those two solutions are identical with each other. If they are different, then solving this equation will lead to two possible values of x, and presumably also two possible values of f(x), so this would not be sufficient. But if they are the same, i.e. if there's really only one solution to this equation, then we would definitely know x, definitely know f(x), and...


GMAT MomentumLike a  tae kwon do blackbelt or an icy road, the GMAT is perhaps most famous for its ability to use your own momentum against you.  Few places is this as evident as on Critical Reasoning questions, in which the most common way to answer incorrectly is to allow your subconscious mind to lead you to a slightly-out-of-scope conclusion that the psychological warriors at GMAC have already anticipated you’d conclude.  Accordingly, to perform well on Critical Reasoning questions it is, well, critical that you pay particular attention to the narrow scope of the conclusion.  As an example, consider the question:

Poor physical fitness among children has become an epidemic among American children.  In Europe, however, where schoolchildren participate in calisthenics and other athletic activities on a daily basis while at school, children are significantly more fit.  Tests show that European students have superior strength and agility, and that they are significantly more likely than are American children to maintain a healthy lifestyle throughout their lives.  Therefore, we must conclude that American children can become more...