We should recognize this as a must be true question, as it asks: If the statements above are true, which one of the following must also be true of trees in the Centerville Botanical Gardens?
This is a stimulus full of comparisons and conditionals. The first sentence gives us a conditional indicated by all, which tells us that if you are tulip trees, then you are older than all the maples. Next, we learn that most, but not all, of the sycamores are also older than all the maples. The last sentence gives us our final conditional that if you are a maple, then you are older than all the dogwoods. Interesting! I think it can be helpful to use some of our sequencing game skills here, and remember that if A is before B, and B is before C, then A is before C. In this case, we are getting a lot of comparison of tree ages, and should think about how they can chain together; I’d expect that the correct answer will be an inference from chaining together these comparisons. Specifically we can form a chain (T AND (most)S → older than M → older than D) from which we can infer that all the tulip trees and most of the sycamores are older than all the dogwoods. Let’s see if this ends up being useful in the answer choices.
Answer Choice (A) This must be false, as we’ve been told all tulips are older than all maples which are older than all dogwoods.
Answer Choice (B) This could be false, as we’ve only been told about the age of the majority of sycamores.
Answer Choice (C) Same as C, we don’t know enough for this to be a certain inference
Answer Choice (D) This could be false as, although we know that some sycamores and all tulips are both older than all maples, we don’t know how the ages of these two groups compare.
Correct Answer Choice (E) Since we’ve been told that not all sycamores are older than all maples, but all tulip trees are, then there must be some sycamores that are younger than all tulip trees.
We have a must be true question here, as the stem demands: If the statements above are true, which one of the following must on the basis of them be true of woolly monkeys in colonies?
This is a very short, straightforward stimulus. Our first sentence begins with the conditional indicator every. If we translate this first conditional, we should see that just being an adult male woolly monkey is enough to be larger than all female woolly monkeys. Our second sentence adds on to this information with another conditional, indicated by the sufficiency indicator any. From this we learn that an adult male woolly monkey is capable of dominating all females. Ok, so the adult males are always larger than and capable of dominating the females, got it. Since this is a must be true question and all our stimulus gives us is two conditionals which cannot be chained, we should expect the inference will either involve a contrapositive or a simple triggering of one of the conditionals leading to its necessary condition. Let’s see what we get.
Answer Choice (A) This answer might be appealing because there seems to be a strong correlation between the men being all larger than the females and all capable of dominating them, but this inference requires that we assume this correlation entails that size is the primary determinant, and there aren’t any other possible determinants which we just haven’t heard about. A must be true inference will never require an assumption.
Answer Choice (B) Our rules have only been about adult males, we can’t infer anything about the adolescents with certainty.
Answer Choice (C) Again we have to read carefully here; we only know about specifically adult males, so we can’t infer this general rule about all males. What if some adolescent males are larger than females but won’t dominate them yet.
Correct Answer Choice (D) This is just the contrapositive of our second rule. If a male doesn’t dominate a female, then the male must not be an adult male.
Answer Choice (E) This must be false, as we’ve been told any adult male will dominate any female; this answer choice would entail that adult males won’t dominate some females.
This is a must be true question, because the stem asks: If the statements above are true, then which one of the following must also be true*?*
The stimulus gives us a period of time, the 16 years between 1973 and 1989, and tells us that three things happened during it; total energy use increased less than 10%, specifically electrical energy use grew by more than 50%, and GNP grew by more than 50%. Important things to note are the distinction between the superset general energy use and the subset electrical energy use, as well as the equivalence in percentage growth between electrical energy use and GNP. On to the answers:
Answer Choice (A) The problem with this answer is we know little about overall energy usage. We know the growth of total energy use and of specifically electrical energy use, but we don’t know how the two compare. Let’s say the total energy was 100J, and it increased by less than 10% to 109J. For all we know electrical energy was only 1J and only grew to 2 J. While electrical energy did grow by more than 50%, it still represents an insignificant portion, less than 2%, of total energy use.
Answer Choice (B) This answer wants you to make a similar error as A and assume that electrical energy represents a significant portion of total energy. If this were true, then the much lower growth of energy overall would suggest a decline of non-electrical energy. But we cannot make these assumptions; the correct answer will be certain given the information in the stimulus.
Correct Answer Choice (C) This answer relies on you correctly inferring that if the growth of a whole is lower than the growth of one of its parts, that part grew proportional to the whole. Since we know that total energy use couldn’t have grown more than 10%, and electrical energy use couldn’t have grown less than 50%, the electrical energy use must have grown as a proportion of total energy use. To use our 100J example, 2J is a greater proportion of 109J than 1J is of 100J.
Answer Choice (D) This answer wants you to infer a stronger connection from a mere correlation. We are not entitled to make the assumptions necessary for that inference.
Answer Choice (E) This answer involves non-electrical energy as well as the relationship between GNP and electrical energy use. Because we aren’t given real insight into either of these things in the stimulus, this is a could be false answer.
We should know this is a weakening question, since it asks us: Which one of the following, if true, most seriously weakens the argument?
This is a 5 star question, and the stimulus throws a lot of stuff to remember at us. The first sentence tells us about a “catch per unit effort” (CPUE) that is used to monitor shark populations in local waters. We are then given a definition of what the CPUE is: it is the number of an individual species of shark that shark-fishing boats catch per hour for each kilometer of net in the water. We’re only two sentences in and we’ve already been given an information overload; South Australia, sharks, catch per unit effort, commercial shark-fishing boats, per hour per km of net. Similar to how low-res summaries are helpful on RC, on dense LR passages it’s helpful to try and translate what’s going on into your own words. Something like “Shark population changes are monitored by how many of a species are caught considering the time and size of net used.”
All of this information so far has just been context on what a CPUE is. Now we are told that there a species of shark whose CPUE has remained constant since 1973. From this the author concludes that the population of the shark species has remained constant since 1973. The major assumption of this argument is that the CPUE of a shark species is an accurate and consistent measure of its actual population changes. While there is always a lot of different ways to weaken an argument, we should expect that this assumption might play a role. An answer that undermines the CPUE’s accuracy and consistency will be a good answer for this question. Let’s see what the answer choices have in store for us:
Answer Choice (A) Always stay anchored in the conclusion. The conclusion we want to weaken specifically specifies that we are interested in the population of the species in the waters around South Australia. Whether or not it is found in other parts of the world is irrelevant.
Answer Choice (B) This might be an appealing answer if your eyes light up at seeing profitable, and you infer that this answer undermines the CPUE because people will only hunt where there are profitable sharks, and maybe the shark species isn’t profitable. The problem is that we don’t know if the species is profitable, and even if it wasn’t profitable we only know that profitable sharks tend to stay in the same spots. Maybe our species isn’t profitable but it is widely dispersed so that it gets caught in the profitable hunting areas. We just don’t have enough information for this answer to weaken the argument.
Answer Choice (C) Interesting! But this answer does nothing to undermine the argument that the CPUE is an accurate indicator of the species real population changes. Even if these nets kill lots of sharks, they still catch them so that we can compare how many are being caught per hour for each kilometer of net.
Answer Choice (D) Again, we just don’t get any information here that can weaken our CPUE is accurate argument. You might want to infer that this would encourage shark-fishers to catch higher numbers of smaller sharks, but that doesn’t affect the CPUE’s accuracy as an indicator of population changes.
Correct Answer Choice (E) What this answer does is give us a reason to believe shark-fishers should be catching a larger portion of shark populations than they did in 1973. If a new device is introduced that should mean higher rates of capture, but the CPUE stays the same, it suggests that the actual population has declined without the CPUE recognizing it. If the population was 20 before but the hunting technology only allowed 1 out of every 10 to be caught, and the population next year declined to 10 but the new device increased the capture rate to 2 out of every 10, the CPUE would stay the same while the population fell by 50%!
This is a Resolve, Reconcile, and Explain Question. We know this because of the question stem, which includes: “...does most to help resolve the discrepancy...” and then gives us exactly what we need to be addressing in the stimulus, which has something to do with predicting the completion of a job. Before we try and understand what that means, we should read the stimulus.
RRE questions will require an explanation of a conflicting set of facts (often 2). Our correct answer choice, when plugged back into the stimulus, will resolve the discrepancy by explaining how the two sides of the apparent conflicting issues actually make sense together. The correct answer will use both sides, though not necessarily explicitly, to explain the conflict. Often, the test will entice you to make naive assumptions about the conflict - don’t fall for it! Your approach should fall under the “this seems wrong because of xyz, but I can think of a few reasons it could work.”
Our first sentence says that officials predicted repaving roads would take municipal road pavers 6 months to complete. They thought it would take a private contractor the same amount of time. However, a private contractor finished in 28 days. Wow - big overestimation by the municipal officials! Now the stem makes a lot more sense.
What could possibly account for this massive difference? A number of things! Perhaps private contractors are able to set their hours and therefore can work at night when roads are less busy, and municipal road pavers are not able to. Maybe the private contractor has a larger crew than the municipality does.
Answer Choice (A) This does not address the predicted vs the actual time it took to complete the project. We need more for this to work. This is out.
Answer Choice (B) This addresses both private contractors and municipal crew. If we were to say that municipal workers can only work 5 days and private contractors set their own hours and can/do work more hours per week than municipals, then this would be great. Alas, it does not. This is out.
Answer Choice (C) This also does not address the difference between the estimated time for completion and the actual time of completion for private contractors.
Answer Choice (D) This actually deepens the issue. If the municipal crew is larger, wouldn’t they work faster? This is out.
Correct Answer Choice (E) This is good - they’re saying municipal workers have a longer process than private contractors and that’s why it takes them longer. The municipal official's estimation of how long it would take the municipal workers could be correct, but assuming the work process is the same for private contractors would inevitably lead them to estimate the wrong amount of time it would take the contractors to finish.
We should recognize this is a most strongly supported question, because the stem asks: Which one of the following is most strongly supported by the information above?
This is a five star question, and getting right is a real test of your ability to recognize the overall issue behind the details and make a key inference. The first sentence is a fairly straight forward conditional, though we should note that it only says that the article can be ruined, not that it will or must be ruined; badly worn needle → article can be ruined. Next we are told that the sewing machine operators in specifically traditional apparel factories monitor their needles and replace those that begin to wear out. We can infer that this practice would prevent at least one potential cause of clothing articles being ruined, but unfortunately we learn sewing operations are becoming increasingly automated, so the operators who monitor needles in traditional factories are being replaced, and it just isn’t efficient to hire people just for monitoring needles. The stimulus ends with a prediction that a new fancy device that detects needle wear is going to become standard equipment of specifically automated apparel factories.
Alright so sewing needles can wear out, and when they do it can ruin the product being sewn. Traditional factories dealt with this problem through human oversight, but since those operators are being replaced in automated factories and it isn’t efficient to hire people who just monitor needles, it seems like there could be a problem. Luckily, it is expected that a new device is going to become standard which uses sound to monitor needle wear, solving the problem. Let’s see what supported inference we get in the answer choices:
Answer Choice (A) This answer is consistent with what we’ve been told, and even might seem to be supported by the prediction of the new device. The problem is that we are only told that the new device is expected to become standard, which means it isn’t certain that it will, while on the other hand we are told that in the traditional factories needles are monitored and replaced. This answer depends on making many assumptions, and is therefore not strongly supported by the information in the stimulus alone.
Answer Choice (B) What we’ve been told actually makes this less likely; human needle monitors aren’t a viable option for an automated factory because it is inefficient to hire people with the sole purpose of monitoring needles.
Answer Choice (C) All we know is that traditional factories don’t use automated equipment instead of human operators for sewing. It is entirely consistent with the stimulus that everything else in traditional apparel factories is automated. This answer requires that we assume a lot about traditional apparel factories that we just don’t know.
Correct Answer Choice (D) This is the correct answer, but it is tricky to pick up on because it relies on making an inference implicit to the stimulus as a whole. The stimulus is all about the problem of needle wear potentially ruining clothing articles, and how humans or devices can be used to monitor needles. If it were true that needle wear occurred at a predictable rate, than it wouldn’t be so important to monitor the needles, since it could be predicted based on the needle’s usage when it would become badly worn. This is a case where maintaining a grasp on the bigger picture of the stimulus is crucial.
Answer Choice (E) This answer is somewhat supported by the fact that it is specifically an acoustic device that can detect needle wear. However, we can’t assume that detection via sound requires that the needles become increasingly loud. What if the noise worn needles make is quieter than good needles? What if it is the same volume but a different kind of noise? This answer wants you to jump on the detail that the devices are acoustic while missing the broader problem and why it supports D.