GMAT Focus Edition

D. 48 km/h

Average speed is Total Distance / Total Time. Let the distance between City A and City B be D. Time to A to B = D/60. Time to B to A = D/40. Total Distance = D + D = 2D. Total Time = D/60 + D/40 = (2D + 3D)/120 = 5D/120 = D/24. Average Speed = 2D / (D/24) = 2D * (24/D) = 48 km/h. This is also a harmonic mean: 2 / (1/60 + 1/40).

A. (0.97)^20

Since the sample size (20) is small compared to the total population (500), and the defect rate is low, we can approximate this as a binomial probability. The probability of one item not being defective is 1 - 0.03 = 0.97. For 20 items to be non-defective, it's (0.97)^20.

C. 2

This is an inverse proportion problem. The total 'worker-days' needed is 3 workers * 15 days = 45 worker-days. To complete the task in 9 days, you need 45 worker-days / 9 days = 5 workers. Since there are already 3 workers, 5 - 3 = 2 additional workers are needed.

B. 97

Let the score on the fourth exam be x. The average of four exams is (Sum of scores) / 4. So, (85 + 92 + 78 + x) / 4 = 88. Summing the known scores: 85 + 92 + 78 = 255. So, (255 + x) / 4 = 88. Multiply both sides by 4: 255 + x = 352. Subtract 255 from both sides: x = 352 - 255 = 97.

A. Both statements together are sufficient, but neither statement alone is sufficient.

Statement (1): x^2 - 5x + 6 = 0. This factors to (x-2)(x-3) = 0, so x = 2 or x = 3. Not sufficient as x could be 2 or 3. Statement (2): x is a prime number. This tells us x could be 2, 3, 5, 7, etc. Not sufficient. Combining (1) and (2): From (1), x is 2 or 3. From (2), x is a prime number. Both 2 and 3 are prime numbers. So, x could still be 2 or 3. Therefore, both statements together are not sufficient to find a unique value for x.

B. 5 liters

Let x be the liters of 60% solution and y be the liters of 30% solution. We have two equations: x + y = 15 (total volume) and 0.60x + 0.30y = 0.40(15) (total acid). From the first, y = 15 - x. Substitute into the second: 0.60x + 0.30(15 - x) = 6. This simplifies to 0.60x + 4.5 - 0.30x = 6, so 0.30x = 1.5, and x = 5.

A. Participation in the mindfulness sessions in the study was entirely voluntary, attracting individuals already predisposed to stress management.

The company assumes that the positive effects observed in a voluntary program will translate to a mandatory one. If the original participants were self-selected and already inclined to benefit, then forcing everyone to participate might not yield the same results, thereby weakening the expectation of increased productivity.

A. The city has recently invested heavily in other infrastructure projects, leading to a strained municipal budget.

The opponents' argument centers on the 'undue burden on taxpayers' due to the 'significant upfront cost.' If the city's budget is already strained by other recent investments, then adding another significant cost would indeed make the burden more 'undue,' thus strengthening their argument.

A. Children with naturally higher concentration skills are more likely to prefer reading physical books over digital devices.

The study suggests that reading physical books *causes* better concentration. To weaken this, one could suggest an alternative cause or reverse causation. Option A proposes reverse causation: it's not that physical books cause concentration, but rather that children who already have good concentration *choose* physical books, thus weakening the study's causal claim.

D. The city center experiences high foot traffic from tourists and local residents, many of whom are art enthusiasts.

To strengthen the *specific link* between location and success, one needs to provide evidence that explains *how* the location contributes to success. Option C describes the mechanism: the prime location in the city center has high foot traffic of the target demographic (art enthusiasts), directly explaining why location would lead to high visitor numbers and sales.

C. The startup's product is a high-end luxury item, typically purchased by an older, wealthier demographic.

The consultant's advice is based on two premises: social media reaches young adults, and young adults are the target demographic. Option B directly undermines the second premise by stating that the startup's product is for an 'older, wealthier demographic', not young adults. If the target demographic is incorrect, then the advice to reach young adults via social media, no matter how cost-effective for that group, is fundamentally flawed for the startup's actual product.

C. For serious athletes, consistently tracking trends in calorie expenditure is more important than precise daily figures.

The magazine's conclusion hinges on the idea that 20% variation makes the tracker unreliable for serious athletes. If serious athletes prioritize trends over precise daily figures, then the 20% variation would not make the device unreliable for their specific needs, thus undermining the conclusion.

D. A severe drought began shortly after the factory opened, significantly lowering the river's water levels.

The environmentalists conclude the factory is *directly responsible* for the fish decline, based on a 'post hoc ergo propter hoc' fallacy (after this, therefore because of this). Option B introduces a strong alternative cause (a severe drought and lowered water levels) that occurred concurrently with the factory's opening, providing a more plausible explanation for the fish decline and weakening the direct causal link to the factory.

D. A recent audit revealed that household and commercial waste, much of which is recyclable, constitutes 70% of the city's total waste stream.

The advocacy group's counter-argument hinges on the premise that 'most of the city's waste is non-recyclable construction debris', implying the recycling program would have a 'negligible impact'. Option B directly refutes this premise by stating that household and commercial waste, which is largely recyclable, constitutes 70% of the total waste. If 70% is recyclable, then the program would likely have a significant, not negligible, impact.

B. The neighboring city's public transportation system is significantly less developed than that of the city considering the program.

The council member's argument is based on an analogy. To challenge an analogical argument, one must show a significant difference between the two cases that undermines the relevance of the comparison. If the neighboring city has poor public transport, then its residents might be more reliant on bike-sharing to replace car trips, whereas the city considering the program might have residents who would switch from public transport to bikes, not cars, thus having less impact on traffic and emissions.

D. The company's primary environmental impact stems from its manufacturing processes, which rely heavily on fossil fuels.

The CEO claims that converting vehicles will *significantly* reduce *overall* environmental impact. To show this is overstated, one must identify another, larger source of environmental impact that the initiative doesn't address. Option B indicates that the company's *primary* impact is from manufacturing, which relies on fossil fuels. If this is the main source of impact, then converting vehicles (a secondary source) will not lead to a *significant overall* reduction, making the CEO's claim overstated.

B. Customers prioritize speed of response over the nature of the interaction (human vs. automated).

Proponents argue for improved customer satisfaction due to *faster response times*. This conclusion relies on the critical assumption that customers value speed *more* than or at least *as much as* they value interacting with a human. If customers prefer human interaction regardless of speed, then faster automated responses would not necessarily lead to improved satisfaction, thus undermining the proponents' argument. Option C directly states this necessary assumption.

D. Many users rely on the tracker's calorie burn data to set precise dietary goals for weight loss.

The manufacturer argues that the 20% overestimation is negligible because users care about *relative* progress, not *absolute* accuracy. To undermine this, one must show that absolute accuracy *is* important to users for their primary goals. If users rely on the data for precise dietary goals for weight loss, then a consistent 20% overestimation is far from negligible; it would actively mislead them and hinder their progress, making absolute accuracy crucial.

D. Whether the 30% reduction in symptoms is considered clinically significant for patients with this disease.

The company concludes the drug is 'effective' based on a 30% symptom reduction. However, 'effective' in a medical context typically means 'clinically significant' or 'meaningful to patient health'. If a 30% reduction, while statistically better than placebo, does not actually improve a patient's quality of life or disease progression in a meaningful way, then the drug would not be truly 'effective' in the practical sense, making this the most important information.

A. A popular local book club recently started focusing exclusively on classic literature, meeting weekly at a cafe near the bookstore.

The bookstore owner observes a correlation and assumes causation. Option B provides a strong alternative cause for the increase in classic literature sales, directly challenging the idea that the art gallery is the primary driver.

D. It assumes that correlation implies causation without considering other factors.

The argument observes a correlation (breakfast and better performance) and then jumps to a causal conclusion (mandatory breakfast will *improve* performance). This is a classic 'correlation does not equal causation' flaw. There could be other factors (e.g., socioeconomic status, parental involvement) that explain both regular breakfast eating and better academic performance.

C. The target demographic for artisanal handcrafted jewelry rarely makes purchasing decisions based on influencer recommendations.

The marketing firm advises influencer marketing for artisanal jewelry based on its effectiveness for 'fashion brands'. Option B directly challenges the core assumption that the behavior of 'fashion brands' consumers applies to the startup's 'artisanal handcrafted jewelry' target demographic. If the target demographic for *this specific product* doesn't respond to influencers, then the advice is seriously weakened, regardless of its effectiveness for general 'fashion brands'.

A. Students who enroll in the online platform are typically self-motivated individuals with a history of academic excellence.

The platform attributes its students' higher scores to its AI-driven modules. Option B introduces a 'self-selection bias' where the students enrolling are already high-achievers. This suggests that the students' inherent motivation and academic history, rather than the AI modules, might be the primary reason for their higher scores, thereby weakening the claim about the AI's effectiveness.

D. Surveys indicate that most smartphone users prioritize camera quality over battery life.

The marketing team's projection hinges on the assumption that 'significantly longer battery life' will be the 'primary driver of sales'. Option B directly challenges this fundamental assumption by stating that users prioritize camera quality. If the primary driver of sales is something other than battery life, then even a superior battery will not necessarily lead to the projected market share increase.

A. Market research shows that consumers are often willing to pay a premium for innovative camera features.

The company's strategy hinges on battery life being the *primary* driver. To challenge this, one must introduce another factor that is also a primary driver, or even more important. Option A suggests that innovative camera features are a strong purchasing driver, directly undermining the uniqueness of battery life as the *primary* factor.