RC 3

New observations about the age of some globular clusters in our Milky Way galaxy have cast doubt on a long-held theory about how the galaxy was formed. The Milky Way contains about 125 globular clusters (compact groups of anywhere from several tens of thousands to perhaps a million stars) distributed in a roughly spherical halo around the galactic nucleus. The stars in these clusters are believed to have been born during the formation of the galaxy, and so may be considered relics of the original galactic nebula, holding vital clues to the way the formation took place.

The conventional theory of the formation of the galaxy contends that roughly 12 to 13 billion years ago the Milky Way formed over a relatively short time (about 200 million years) when a spherical cloud of gas collapsed under the pressure of its own gravity into a disc surrounded by a halo. Such a rapid formation of the galaxy would mean that all stars in the halo should be very nearly the same age.

However, the astronomer Michael Bolte has found considerable variation in the ages of globular clusters. One of the clusters studied by Bolte is 2 billions years older than most other clusters in the galaxy, while another is 2 billion years younger. A colleague of Bolte contends that the cluster called Palomar 12 is 5 billion years younger than most other globular clusters.

To explain the age differences among the globular clusters, astronomers are taking a second look at "renegade" theories. One such newly fashionable theory, first put forward by Richard Larson in the early 1970's, argues that the halo of the Milky Way formed over a period of a billion or more years as hundreds of small gas clouds drifted about, collided, lost orbital energy, and finally collapsed into a centrally condensed elliptical system. Larson's conception of a "lumpy and turbulent" protogalaxy is complemented by computer modeling done in the 1970's by mathematician Alan Toomre, which suggests that closely interacting spiral galaxies could lose enough orbital energy to merge into a single galaxy

1. The passage is primarily concerned with discussing 
(A) the importance of determining the age of globular clusters in assessing when the Milky Way galaxy was formed 
(B) recent changes in the procedures used by astronomers to study the formation of the Milky Way galaxy 
(C) current disputes among astronomers regarding the size and form of the Milky Way galaxy 
(D) the effect of new discoveries regarding globular clusters on theories about the formation of the Milky Way galaxy 
(E) the origin, nature, and significance of groups of stars known as globular clusters 

2. According to the passage, one way in which Larson's theory and the conventional theory of the formation of the Milky Way galaxy differ is in their assessment of the 
(A) amount of time it took to form the galaxy 
(B) size of the galaxy immediately after its formation 
(C) the particular gases involved in the formation the galaxy 
(D) importance of the age of globular clusters in determining how the galaxy was formed 
(E) shape of the halo that formed around the galaxy

3. Which of the following, if true, would be most useful in supporting the conclusions drawn from recent observations about globular clusters? 
(A) There is firm evidence that the absolute age of the Milky Way galaxy is between 10 and 17 billion years. 
(B) A survey reveals that a galaxy close to the Milky Way galaxy contains globular clusters of ages close to the age of Palomar 12. 
(C) A mathematical model proves that small gas clouds move in regular patterns. 
(D) Space probes indicate that the stars in the Milky Way galaxy are composed of several different types of gas. 
(E) A study of over 1,500 individual stars in the halo of the Milky Way galaxy indicates wide discrepancies in their ages.

[Reveal] Spoiler:

4. If Bolte and his colleague are both correct, it can be inferred that the globular cluster Palomar 12 is approximately 
(A) 5 billion years younger than any other cluster in the galaxy 
(B) the same age as most other clusters in the galaxy 
(C) 7 billion years younger than another cluster in the galaxy 
(D) 12 billion years younger than most other clusters in the galaxy 
(E) 2 billion years younger than most other clusters in the galaxy

5. The passage suggests that Toomre's work complements Larson's theory because it 
(A) specifies more precisely the time frame proposed by Larson 
(B) subtly alters Larson's theory to make it more plausible 
(C) supplements Larson's hypothesis with direct astronomical observations 
(D) provides theoretical support for the ideas suggested by Larson 
(E) expands Larson's theory to make it more widely applicable 

6. Which of the following most accurately states a finding of Bolte's research, as described in the passage? 
(A) The globular clusters in the Milky Way galaxy are 2 billion years older than predicted by the conventional theory. 
(B) The ages of at least some globular clusters in the Milky Way galaxy differ by at least 4 billion years. 
(C) One of the globular clusters in the Milky Way galaxy is 5 billion years younger than most others. 
(D) The globular clusters in the Milky Way galaxy are significantly older than the individual stars in the halo. 
(E) Most globular clusters in the Milky Way galaxy are between 11 and 15 billion years old. 

7. The author of the passage puts the word "renegade" (line 29) in quotation marks most probably in order to 
(A) emphasize the lack of support for the theories in question 
(B) contrast the controversial quality of the theories in question with the respectable character of their formulators 
(C) generate skepticism about the theories in question 
(D) ridicule the scientists who once doubted the theories in question 
(E) indicate that the theories in question are no longer as unconventional as they once seemed

RC 2 Answers

1.
"Except" questions require us to test the five answer choices to determine the "odd
one out." It is beneficial to use the True / False technique: label each answer choice
with a T or an F and look for the odd one out (which, in this case, we should expect
to be an F).
(A) True. The third sentence of the second paragraph characterizes changing
weather patterns due to global warming as a subtle effect of human activities.
(B) True. The first two sentences of the second paragraph classify both toads and
frogs as amphibians. Later in the second paragraph, the passage explains that
amphibians have permeable skin.
(C) True. The third sentence of the second paragraph states explicitly that scientists
"hypothesize" that human activity is responsible for the global decline of amphibious
populations. Since a hypothesis is an educated guess rather than a fact, it is true
that human activity may not be responsible for the decline.
(D) True. The second sentence of the first paragraph states that money was raised
in the United States to establish the Monteverde Cloud Forest Preserve.
(E) CORRECT. False. The passage offers no information about the number of
salamander species in Costa Rica that have disappeared since the late 1980s. We
cannot assume that this omission indicates a lesser number than either toad or frog
species.
2.
The correct answer to an inference question on the GMAT must be supported by
evidence from the text without need for external information.
(A) The passage states that twenty of the fifty species of frogs and toads known to 
once inhabit a 30-square-kilometer area near Monteverde have disappeared. 
Nothing is implied about the areas of Costa Rica farther from Monteverde. 

(B) CORRECT. The passage suggests that amphibians are able to offer humans 
early notification of the deterioration of the environment because of the amphibians' 
permeable skin. Thus, permeable skin must be a characteristic that humans do not 
possess. 

(C) No causal relationship between the build-up of pollutants in the atmosphere and 
a decrease in atmospheric ozone is suggested in the passage. 

(D) The author states that humans would be wise to heed the warning offered by the 
decline of amphibious populations, but nothing suggests that humans normally do 
not take signals of environmental deterioration seriously. 

(E) The passage does not compare Costa Rica's environmental problems to those of 
other countries. 

3. 
In the second paragraph, the author mentions "the more subtle effects of human 
activity on the world's ecosystems," and then lists three of these effects: the build-up 
of pollutants, the decrease in atmospheric ozone, and changing weather patterns 
due to global warming, all of which, scientists hypothesize, "are beginning to take 
their toll." The key to answering this question correctly is to recognize, in context, 
what these effects have in common. 

(A) Nowhere does the passage suggest or imply that these changes are not easily 
recognized by sophisticated testing equipment. 

(B) CORRECT. All of these effects happen on a global scale, so their immediate 
consequences on specific ecosystems are difficult to recognize. Furthermore, the 
passage states these effects are "beginning to take their toll," indicating that the 
effects happen over time. 

(C) Scientists hypothesize that these effects do affect amphibians, but nothing in the 
passage indicates that only small animal species such as amphibians are affected. 
In fact, the final sentence of the passage indicates that humans too might be affected 
by these environmental changes. 

(D) The passage states that scientists hypothesize about the consequences of these 
subtle effects; this indicates that scientists do in fact discuss these effects. 

(E) The passage indicates that the consequences of these effects are global, 
causing disruptions in amphibious populations "the world over." 

4. 
This question is really just a disguised inference question. The correct answer to an 
inference question must be directly supported by evidence from the text. 
(A) CORRECT. The first sentence of the passage states that the beauty of Costa 
Rica's golden toad was one factor that generated interest from a public normally 
unconcerned with amphibians. Thus, many amphibians must not be considered 
beautiful. 

(B) The passage indicates that habitat preservation in isolation - no matter the size of 
the habitat - was not enough to save the golden toad. Instead, scientists theorize that 
broader ecological issues are harming the world's amphibious populations. 

(C) The second paragraph tells us that amphibian populations have been declining 
around the world. 

(D) This is a misinterpretation of the analogy used in the second paragraph. The 
author is implying that amphibians may provide humans an early warning for 
detrimental changes to the environment, just as canaries provide humans an 
indication of detrimental conditions in coal mines. 

(E) The final sentence of the passage indicates that humans would be wise to 
recognize the potential environmental deterioration signified by declining amphibious 
population, but it is too extreme to infer that no humans consider this decline a threat 
to humans. In fact, the author of the passage seems to consider it a threat! 

5. 
The first paragraph of the passage discusses a specific case in which a particular 
amphibian mysteriously disappeared from its habitat and suggests that humans may 
have been in some way responsible for its demise. The second paragraph explains 
that declining amphibious populations are actually a global trend and hypothesizes 
that a variety of human activities are harming these environmentally sensitive 
animals. 

(A) The example of the golden toad is too narrow and specific to be the primary 
purpose of the passage. Instead, the golden toad is used as an example of a much 
larger trend. 

(B) Though this answer choice is on the right track, it is too extreme to say that 
human activity is "undoubtedly" to blame for the global decline of amphibian 
populations. Instead the passage indicates that scientists "hypothesize" that human 
activity is responsible. 

(C) An attempt to convince humans to minimize the output of pollutants is never 
mentioned in the passage. 

(D) CORRECT. The passage discusses the mysterious disappearance of 
amphibious populations worldwide and hypothesizes that subtle effects on 
ecosystems resulting from human activity may be responsible for these 
disappearances. 

(E) The final sentence of the passage does urge humans to pay attention to 
declining amphibian populations, but this is not the primary purpose of the passage. Moreover, the passage specifically discusses amphibians, while this answer choice 
broadly mentions "important environmental changes" rather than focusing on 
amphibians. 

RC 2

The golden toad of Costa Rica, whose beauty and rarity inspired an unusual degree of human interest from a public generally unconcerned about amphibians, may have been driven to extinction by human activity nevertheless. In the United States, a public relations campaign featuring the toad raised money to purchase and protect the toad's
habitat in Costa Rica, establishing the Monteverde Cloud Forest Preserve in 1972. Although this action seemed to secure the toad's future, it is now apparent that setting aside habitat was not enough to save this beautiful creature. The toad's demise in the late 1980s was a harbinger of further species extinction in Costa Rica. Since that time, another twenty of the fifty species of frogs and toads known to once inhabit a 30 square kilometer area near Monteverde have disappeared.

The unexplained, relatively sudden disappearance of amphibians in Costa Rica is not a unique story. Populations of frogs, toads, and salamanders have declined or isappeared the world over. Scientists hypothesize that the more subtle effects of human activities on the world's ecosystems, such as the build-up of pollutants, the decrease in atmospheric ozone, and changing weather patterns due to global warming, are beginning to take their toll. Perhaps amphibians - whose permeable skin makes them sensitive to environmental changes - are the "canary in the coal mine," giving us early notification of the deterioration of our environment. If amphibians are the biological harbingers of environmental problems, humans would be wise to heed their warning.

1. According to the passage, all of the following are true EXCEPT:
· Humans are at least partially responsible for changing weather patterns.
· Toads, like frogs, have permeable skin.
· Human activity is not necessarily responsible for the global decline of amphibious populations.
· Costa Rica's Monteverde Cloud Forest Preserve was not paid for solely by the Costa Rican government.
· More frog and toad species than salamander species have disappeared in Costa Rica since the late 1980s.

2. It can be inferred from the passage that
· only thirty species of frogs and toads remain in Costa Rica
· humans do not have permeable skin
· the build-up of pollutants in the atmosphere causes a decrease in atmospheric ozone
· humans do not usually take signals of environmental deterioration seriously
· Costa Rica suffers from more serious environmental problems than many other countries

3. The author uses the adjective "subtle" in the second paragraph most probably to emphasize that
· these effects are not easily recognized by sophisticated testing equipment
· these effects are difficult to notice because they take place over time on a global scale
· these effects are so minimal that they affect only small animal species such as amphibians
· these slight effects of human activity are rarely discussed by scientists
· these effects are infrequently observed because they affect only specific world regions

4. The passage implies that
· many amphibians are not considered beautiful.
· the Monteverde Cloud Forest Preserve was not large enough to protect the golden toad.
· only Costa Rican amphibians living near Monteverde have disappeared since the 1980s.
· amphibians sometimes live in coal mines.
· no humans yet consider the decline of amphibious populations an indication of a threat to human populations.

5. The primary purpose of the passage is to
· discuss the mysterious disappearance of Costa Rica's golden toad.
· explain why human activity is undoubtedly to blame for the global decline of amphibious populations
· convince humans that they must minimize the global output of pollutants.
· describe the recent global decline of amphibious populations and hypothesize about its causes.
· urge humans to pay careful attention to important environmental changes.

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RC 1 Answers ADAB

1. 

Questions that ask about "primary purpose" must take into account the passage in 
its entirety. Overall, this passage is about the differing predictive uses of the 
various economic indicators. 

(A) CORRECT. The passage does indeed focus on the utility of "various economic 
indicators." 

(B) This choice mistakenly focuses on a process that is not discussed in the 
passage. 

(C) This choice focuses only on a few sentences in the last paragraph of the 
passage. 

(D) This choice mischaracterizes the intent of the passage in using the verb "trace", 
which implies a chronology. 
(E) This choice is incorrect in describing the author's purpose with the verb "to 
argue." The author does not present an argument in the passage, but rather an 
objective comparison. 


2. 
The third paragraph states that mortgage applications and profit margins are 
examples of leading indicators, which have the greatest predictive power. 
Therefore, we need to find an answer choice that relates to either mortgage 
applications or profit margins. 

(A) This choice focuses on the employment rate, which is a coincident indicator 
(paragraph 2). 

(B) This choice focuses on the number of new homes being built, which is not 
discussed in the passage. Do not assume that the number of new homes being built 
can be correlated with mortgage applications, which are indeed a leading indicator 
(paragraph 3). 


(C) This choice focuses on manufacturing, which is a coincident indicator (paragraph 
2). 

(D) CORRECT. Imminent changes in the economic cycle are indicated by leading 
indicators, of which profit margins are an example (paragraph 3). The increase 
described in this choice is indeed a profit margin (revenue minus cost). 

(E) This choice focuses on bankruptcies, which are not mentioned in the passage. 


3. 
In the last paragraph, the author writes: "Establishing a solid framework for 
understanding the behavior of these indicators helps economists to avoid 
miscalculations and to guide the country through periods of slow or negative 
economic growth." 

(A) CORRECT. This choice is consistent with the information contained in the last 
paragraph. 

(B) This choice focuses only on a subpart of this analysis: the role of the indicators 
for the private investor. 

(C) This choice is not reflected in the passage. 

(D) This choice focuses only on downturns whereas the indicators are used for either 
upward or downward economic change. 

(E) This choice is not reflected in the passage. 

4. Lagging indicators have no predictive power. They serve simply as confirmation of 
the recent state of the economy. Therefore, lagging indicators would not be helpful in 
determining future courses of action. 

(A) This does not require predictive power. 

(B) CORRECT. This choice – cutting costs to avoid short-term losses – requires 
predictive power. And so lagging indicators would not be helpful in determining 
whether companies should follow this course of action. 

(C) This does not require predictive power. 

(D) This does not require predictive power. 

(E) This does not require predictive power.
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RC 1

American economists continually attempt to gauge the health of the economy, both for the gain of the private sector as well as for the global standing of the United States. Different elements of the economy react differently to changes in prosperity. Some elements rise and fall as the economy waxes and wanes. These are known as coincident indicators. Other elements are known as leading indicators and usually show a downturn before the economy does. A third group of elements are known as lagging indicators and lose vigor only after the economy has already begun to slow. Economists can predict the direction of the economy by monitoring these indicators.

Coincident indicators, such as manufacturing and employment rates, are the best gauge of the current state of the economy. A continued shift in these indicators allows economists to determine whether the economy itself is in the process of an upturn or a downturn. These indicators coincide with shifts in the economy because they are dependent on sustained prosperity. But since coincident indicators reflect only the current state of the economy, they are not especially useful in predicting how the economy will perform in the near future. Economists must look to other indicators for that.

The indicators with the greatest predictive power are leading indicators, such as mortgage applications and profit margins. When these indicators rise or fall, economists can often foretell similar changes in the country's economic health. These indicators do not cause changes in the economy. Rather, they often signal changes in economic behavior that lead to shifts in the economic cycle. By contrast, the third type of indicator – lagging indicators – is useless as a harbinger of change. But these indicators can be helpful in confirming the assessments of economists.

Determining which elements of the economy fall into which category of indicator requires analysis of copious data and an understanding of the factors that propel the economy. One must determine which events surrounding a turn in the business cycle actually contributed to the change. Establishing a solid framework for understanding the behavior of these indicators helps economists to avoid miscalculations and to guide the country through periods of slow or negative economic growth.

1. The primary purpose of the passage is to
· compare the utility of various economic indicators
· explain the process by which economists draw conclusions about key factors of economic change
· present a conceptual framework used by economists to prescribe economic goals
· trace the development of a set of economic devices
· argue for the continued evaluation of economic factors affecting the business cycle

2. The information in the passage suggests that which of the following would most strongly indicate an imminent change in the business cycle?
· a decrease in the employment rate
· a decrease in the number of new homes built per month
· an increase in the number of new automobiles produced each month
· an increase in the difference between manufacturing costs and retail revenues for large home appliances
· a decrease in the number of corporate bankruptcies per month

3. According to the passage, the main purpose of economic indicators is which of the following?
· to facilitate the analysis necessary to maintain forward economic momentum
· to allow investors to time their investments in sync with economic cycles
· to foster healthy economic competition among various commercial sectors
· to bring to light several key factors in economic downturns
· to promote widespread understanding of economic principles

4. The passage suggests that lagging indicators would be least helpful in determining which of the following?
· whether predictions based on the behavior of the mortgage market were accurate
· whether companies ought to cut costs in order to avoid short-term losses
· whether recent trends in the employment rate were consistent with the overall economic picture
· whether financial analysts are correct in their assessment of recent economic developments
· whether the government was justified in taking action to boost the economy

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