GMAT Avengers Study Group: Must Be True/Inference/Conclusion CR Questions:

by on December 1st, 2014

On GMAT Critical Reasoning, the “big three” question types are (1) find the assumption, (2) strengthen the argument, and (3) weaken the argument. Among the remaining question, this type, the Conclusion/Inference question, is one of the most common. Prompts for this type include questions such as these:

Which of the following must be true on the basis of the politician’s statements above?

Which of the following conclusions is most strongly supported by the information above?

If the above statements are true, which of the following inferences is best supported by them?

In this question type, the prompt presents statements P & Q & R, and our job is to draw a conclusion or inference that is best supported by these statements.

Virtually all the incorrect answer choices of this type follow the same pattern. In plain language, they go too far.  Virtually all the incorrect answer choices will require some kind of additional assumption, over and above the individual statements made in the prompt.

Key Strategies for effectively solving Inference/Must Be True/Conclusion CR problems

  1. Know how to recognize this type. The question stem will typically use some variation of the word conclusion or infer. It will also mention something along the lines of most properly drawn or best supported by. Be careful about one thing: Inference questions can sometimes include the words strongly supports and this language also shows up in Strengthen questions. If the question contains this language, check to see whether it refers to the answers as conclusions or inferences “ if so, this is an Inference question, not a Strengthen question. (Strengthen questions will contain a conclusion in the argument, not in the answer choices.)
  2. Know what to do with Inference questions. The argument will contain fact-based premises and no conclusion. Our goal is to find an answer that must be true given some or all of the premises. We don’t need to use all of the information in the argument.
  3. Do watch out for traps! The answer choices usually contain Real World inferences: things that might be or are even likely to be true in the real world but they don’t absolutely have to be true. These are tricky because we’re used to making reasonable assumptions in the real world when drawing a conclusion or inference “ but we can’t do that on the GMAT.

The following are the links to the articles from our Facebook Event Page that cover good information with respect to effectively tackling these kinds of questions.

In order to understand the overall CR process in general and the different questions types, click here.

Practice Problems

1) Five years ago, McDonald’s made a big mistake by selling off its Chipotle stake to refocus on its core products. Today Chipotle has a market cap of $9 billion (10 percent that of McDonald’s) and the revenue growth it generated during these five years would have more than doubled McDonald’s total revenue growth.

If the information given above is true, which of the following must be true?

(A) If the ratio of revenue to market cap for McDonald’s has remained equal to that of Chipotle in the last five years, then Chipotle has grown at a significantly faster rate than McDonald’s.

(B) Chipotle’s current revenues must be less than the current revenues of McDonald’s.

(C) If market cap is directly proportional to the revenue of a company, then Chipotle must have more than doubled its market cap in the last five years.

(D) The ratio of revenue to market cap for McDonald’s is significantly lower than that for Chipotle.

(E) If both Chipotle and McDonald’s continue to grow at the same pace, then Chipotle will have greater revenues than McDonald’s within the next 10 years.

2) These days, drug companies and health professionals alike are focusing their attention on cholesterol in the blood. The more cholesterol we have in our blood, the higher the risk that we shall die of a heart attack. The issue is pertinent since heart disease kills more North Americans every year than any other single cause. At least three factors—smoking, drinking and exercise- can each influence levels of cholesterol in the blood.

Which one of the following can be properly concluded from the passage?

(A) If a person has low blood cholesterol, then that person’s risk of fatal heart disease is low.

(B) Smoking in moderation can entail as great a risk of fatal heart disease as does heavy smoking.

(C) A high-cholesterol diet is the principal cause of death in North America.

(D) The only way that smoking increases one’s risk of fatal heart disease is by influencing the levels of cholesterol in the blood.

(E) The risk of fatal disease can be altered by certain changes in lifestyle.

3) Public Health Official: After several years of vaccinating all of the citizens of this state for Tacitus’ Disease, a highly infectious virus, state hospitals have cut costs by no longer administering this vaccine, starting at the beginning of this year. A state senator defended the position, arguing that after several years with zero incidence of the disease in the state, its citizens were no longer at risk. This is a flawed argument. Our state imports meats and produce from countries with high incidences of diseases for which our country has vaccines. Three years ago, when we reduced the use of the Salicetiococcus vaccines, a small outbreak of Salicetiococcus among young children, fortunately without fatalities, encouraged us to resume use at the previous vaccines.

The public health official’s statements, if true, best support which of the following as a conclusion?

(A) Young children of the state will be at risk for Tacitus’ Disease.

(B) Some of the meats imported to this state do not have adequate refrigeration during the shipping process.

(C) Tacitus’ Disease is a much deadlier disease than Salicetiococcus, and has a correspondingly higher fatality rate.

(D) No food products produced within the state bear any contaminants that could lead to either Tacitus’ Disease or Salicetiococcus.

(E) The cost of providing all citizens of the state with the Tacitus’ Disease vaccine places an undue burden on the budget of state health agencies.

4) Diamond Enterprises is a store in Apisville that sells specialty luxury items. For several years, Diamond reaped substantial profits and was considering building branch stores in nearby counties. Stibium Industries, for several years the single largest employer in Apisville and the surrounding region, abruptly closed its plant last year, causing widespread unemployment.  Only a fraction of the former Stibium workers have found new jobs, and many of these at much lower wages. Early this year, Diamond Enterprises has filed for Chapter 11 bankruptcy, citing the closure of Stibium as one of the primary causes.

Which of the following inferences is best supported by the passage?

(A) Diamond Enterprises would have avoided bankruptcy if it had followed through with the plan to build branch stores during its more prosperous years.

(B) Stibium’s management team had a corporate account with Diamond Enterprises, and ordered several luxury items used in business meetings and to entertain prospective clients.

(C) Diamond’s direct competitors, in Apisville and in the surrounding region, are much larger than Diamond, and therefore benefitted substantially from the conditions that arose after Stibium closed.

(D) The closure of Stibium resulted in a loss of revenue for Diamond Enterprises.

(E) After Stibium Industry closed, Diamond Enterprises was the single largest employer in Apisville.

5) Wild cheetahs live in the African grasslands. Previous estimates of the size that the wild cheetah population must be in order for these animals to survive a natural disaster in the African grasslands region were too small, and the current population barely meets the previous estimates. At present, however, there is not enough African grassland to support a wild cheetah population larger than the current population.

The statements above, if true, most strongly support which one of the following conclusions?

(A) Previous estimates of the size of the existing wild cheetah population were inaccurate.

(B) The cheetah’s natural habitat is decreasing in size at a faster rate than is the size of the wild cheetah population.

(C) The principal threat to the endangered wild cheetah population is neither pollution nor hunting, but a natural disaster.

(D) In the short term, the wild cheetah population will be incapable of surviving a natural disaster in the African grasslands.

(E) In regions where land is suitable for cheetah habitation, more natural disasters are expected to occur during the next decade than occurred during the past decade.

6) A new medical procedure replaces all three of the tiny bones in the inner ear with a single piece of ultra-thin fiberglass. The procedure has been found to greatly improve hearing in people who have experienced damage to these bones, though it is useless to people whose hearing loss stems from a neurological malfunction. This procedure will benefit a relatively small percentage of the hearing-impaired population.

Which of the following can be concluded from the argument above?

(A) It is possible to hear without the use of the three tiny bones in the inner ear.

(B) Most hearing loss is due to neurological malfunctioning.

(C) More people have impaired hearing because of neurological damage than because of damage to the tiny bones of the inner ear.

(D) Hearing loss due to neurological damage is more severe than hearing loss due to damage to the tiny bones in the inner ear.

(E) The use of fiberglass cannot help people who have lost hearing due to neurological damage.

7) From 1994 to 2001, violent crime in New York City steadily decreased by over 50%, from a rate of 1,861 violent crimes per 100,000 people in 1994 down to 851 violent crimes per 100,000 people in 2001. Criminologists have partially attributed this drop to proactive policing tactics such as “broken window po-licing,” wherein city officials immediately fixed small acts of vandalism and, as a result, lowered other types of criminal behavior. During this same period, the rate of violent crime in the United States steadily decreased by 28% (down to 500 violent crimes per 100,000 people).

Which of the following conclusions is best supported by the information above?

(A) The decrease in the total crime rate in the United States caused the decrease in New York City’s crime rate.

(B) New York City spends more per capita on law enforcement than does the rest of the United States.

(C) If the rest of the United States were to adopt law enforcement tactics similar to those of New York City, national violent crime rates would continue to fall.

(D) Between 1994 and 2001, the violent crime rate in New York City was consistently higher than the national average.

(E) The violent crime rate in New York City will soon be below the national average.

8) Editorial: The government claims that the country’s nuclear power plants are entirely safe and hence that the public’s fear of nuclear accidents at these plants is groundless. The government also contends that its recent action to limit the nuclear industry’s financial liability in the case of nuclear accidents at power plants is justified by the need to protect the nuclear industry from the threat of bankruptcy. But even the government says that unlimited liability poses such a threat only if injury claims can be sustained against the industry; and the government admits that for such claims to be sustained, injury must result from nuclear accident. The public’s fear, therefore, is well founded.

If all the statements offered in support of the editorial’s conclusion correctly describe the government’s position, which one of the following must also be true on the basis of those statements?

(A) The government’s claim about the safety of the country’s nuclear power plant is false.

(B) The government’s position on nuclear power plants is inconsistent.

(C) The government misrepresented its reasons for acting to limit the nuclear industry’s liability.

(D) Unlimited financial liability in the case of nuclear accidents poses no threat to the financial security of the country’s nuclear industry.

(E) The only serious threat posed by a nuclear accident would be to the financial security of the nuclear industry.

9) Studies have shown that moderate consumption of red wine by those of legal drinking age reduces their susceptibility to cancer in the future. Researchers speculate that this is because red wine is rich in the chemical resveratrol. Low levels of resveratrol are associated with high levels of cytochrome P450 isoenzymes, a chemical family whose members are potentially carcinogenic.

Which one of the following statements is most strongly supported by the information above?

(A) An increased risk of cancer is correlated with low levels of cytochrome P450 isoenzymes.

(B) A decreased risk of cancer is correlated with moderately increased levels of resveratrol.

(C) An increased propensity for cancer is correlated with decreased levels of cytochrome P450  isoenzymes.

(D) A decreased propensity for cancer is correlated with low levels of resveratrol.

(E) Cancer is prevented by ingestion of resveratrol in quantities sufficient to prevent a decline in the levels of cytochrome P450 isoenzymes.

10) When a polygraph test is judged inconclusive, this is no reflection on the examinee. Rather, such a judgment means that the test has failed to show whether the examinee was truthful or untruthful. Nevertheless, employers will sometimes refuse to hire a job applicant because of an inconclusive polygraph test result.

Which of the following conclusions can most properly be drawn from the information above?

(A) Most examinees with inconclusive polygraph test results are in fact untruthful.

(B) Polygraph tests should not be used by employers in the consideration of job applicants.

(C) An inconclusive polygraph test result is sometimes unfairly held against the examinee.

(D) A polygraph test indicating that an examinee is untruthful can sometimes be mistaken.

(E) Some employers have refused to consider the results of polygraph tests when evaluating job applicants.

11) In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Which of the following must be true on the basis of the statements above?

(A) There were fewer cases of schistosomiasis last year than five years ago.

(B) The percentage of disease cases from malaria has increased over the past 5 years.

(C) Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%.

(D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis.

(E) If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%.

12) Snowmaking machines work by spraying a mist that freezes immediately on contact with cold air. Because the sudden freezing kills bacteria, QuickFreeze is planning to market a wastewater purification system that works on the same principle. The process works only when temperatures are cold, however, so municipalities using it will still need to maintain a conventional system.

Which of the following, if true, provides the strongest grounds for a prediction that municipalities will buy QuickFreeze’s purification system despite the need to maintain a conventional purification system as well?

(A) Bacteria are not the only impurities that must be removed from wastewater.

(B) Many municipalities have old wastewater purification systems that need to be replaced.

(C) Conventional wastewater purification systems have not been fully successful in killing bacteria at cold temperatures.

(D) During times of warm weather, when it is not in use, QuickFreeze’s purification system requires relatively little maintenance.

(E) Places where the winters are cold rarely have a problem of water shortage.

Answer Key

  1. A
  2. E
  3. A
  4. D
  5. D
  6. A
  7. D
  8. B
  9. B
  10. C
  11. E
  12. C

Make sure you check out the event Facebook page to see all the comments that were being exchanged during the live session.

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1 comment

  • Hi Rahul,

    I wanted to understand how do I become a part of GMAT Avengers club and participate in your facebook sessions. I tried the FB page but wasn't able to.

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