Thick concrete walls insulate well and houses built with them cost less to heat and cool than wooden houses do....

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Logically Completes

HARD

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Thick concrete walls insulate well and houses built with them cost less to heat and cool than wooden houses do. Researchers compared a wooden house with a concrete house that was otherwise identical in every significant way (sun exposure, size, heating and cooling system, etc.). Over a year, monthly energy costs averaged $55 less for the concrete house. In practice, most people choosing a concrete house over a wooden one would probably realize still greater monthly savings on energy, because ____________.

Which of the following most logically completes the passage?

the houses in the survey were built in a region that has winters that are slightly cooler on average, and summers that are slightly warmer on average than is typical of most regions in the country

the heating and cooling systems in the houses in the survey were typical of those found in the average house in the area in which they were built

the wood used in building the wooden house in the survey had high insulating properties created by an experimental treatment that is generally regarded as too expensive for residential construction

the energy efficiency of houses with concrete walls varies greatly depending on the thickness of the walls, with relatively thin concrete walls providing only slightly greater energy efficiency than well-built wooden walls

for the first forty years or so after they are built, maintenance costs for houses built with thick concrete walls tend to be lower than maintenance costs for comparable houses built with wooden walls

Solution

Passage Analysis:

Text from Passage	Analysis
Thick concrete walls insulate well and houses built with them cost less to heat and cool than wooden houses do.	What it says: Concrete houses are cheaper to heat and cool than wooden houses because concrete insulates better What it does: Sets up the basic claim about concrete vs. wooden houses What it is: Author's opening claim Visualization: Wooden house energy costs: $200/month, Concrete house energy costs: $150/month
Researchers compared a wooden house with a concrete house that was otherwise identical in every significant way (sun exposure, size, heating and cooling system, etc.).	What it says: Scientists did a controlled experiment comparing concrete and wooden houses, keeping everything else the same What it does: Introduces evidence to back up the opening claim about concrete being better What it is: Study description
Over a year, monthly energy costs averaged $55 less for the concrete house.	What it says: The concrete house saved $55 per month compared to the wooden house What it does: Provides the specific data that proves concrete houses cost less to run What it is: Study finding Visualization: Wooden house: $200/month, Concrete house: $145/month, Savings: $55/month
In practice, most people choosing a concrete house over a wooden one would probably realize still greater monthly savings on energy, because ______.	What it says: Real-world concrete house buyers would likely save even more than the $55 found in the study What it does: Shifts from the controlled study to real-world situations, suggesting the study underestimated savings What it is: Author's prediction with blank to complete

Argument Flow:

The argument starts with a general claim about concrete houses being more energy efficient, then provides specific research evidence showing $55 monthly savings, and finally suggests real-world savings would be even greater than what the study found.

Main Conclusion:

In real life, people who choose concrete houses over wooden ones would save more than $55 per month on energy costs.

Logical Structure:

The controlled study provides a baseline of $55 savings, but the author argues this is actually the minimum savings people would see - real conditions would produce even better results than this controlled experiment.

Prethinking:

Question type:

Logically Completes - We need to find a statement that logically explains why real-world concrete house buyers would save MORE than the $55/month found in the controlled study.

Precision of Claims

The key claim is quantitative and comparative - people in practice would save MORE than $55/month (which was the controlled study result). We need to explain why real-world conditions would lead to greater savings than the controlled experiment showed.

Strategy

Since the argument says real people would save MORE than the study showed, we need to think about what aspects of real-world house selection differ from the controlled study that would increase the energy savings advantage of concrete houses. The study kept everything identical except wall material, so we need reasons why real-world buyers might not keep everything else identical, in ways that favor concrete houses even more.

Answer Choices Explained

the houses in the survey were built in a region that has winters that are slightly cooler on average, and summers that are slightly warmer on average than is typical of most regions in the country

This talks about the study location having slightly more extreme temperatures than average. However, more extreme weather would actually increase the energy efficiency advantage shown in the study, not decrease it. If anything, this would suggest the study overestimated rather than underestimated savings, which contradicts the argument's claim that real-world savings would be greater.

the heating and cooling systems in the houses in the survey were typical of those found in the average house in the area in which they were built

This states that the heating and cooling systems were typical of the area. This doesn't explain why real-world buyers would save more than the study showed - if the systems were already typical, there's no reason to expect different results in practice. This choice provides no mechanism for why real-world savings would exceed $55/month.

the wood used in building the wooden house in the survey had high insulating properties created by an experimental treatment that is generally regarded as too expensive for residential construction

This explains that the wooden house in the study used experimentally treated wood with superior insulating properties that's too expensive for normal construction. This is perfect because it means the study actually tested concrete houses against an unusually efficient wooden house. In real life, people would be comparing concrete houses to regular wooden houses without this expensive treatment, so the concrete house advantage would be even greater than the $55/month found in the study.

This discusses how concrete wall thickness affects efficiency, noting that thin concrete walls only slightly outperform wooden walls. This would suggest that real-world concrete houses (which might have thinner walls) would perform worse than the study house, contradicting the argument's claim that real-world savings would be greater.

This is about maintenance costs over 40 years, not energy costs. While this might make concrete houses more attractive overall, it doesn't explain why monthly energy savings specifically would be greater than the $55/month found in the study.

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