Thick concrete walls insulate well and houses built with them cost les

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Updated the tag. ­Thank you.

 

­A boy-o-boy wordy FIB question, all the modifiers are so important to understand this argument, and we can cut very little fluff during the analysis of this question.

Passage analysis:
Conclusion: The author claims that: in practice, people choosing a concrete house instead of a wooden house will probably have still greater savings than the $55 monthly savings claimed by the researchers.

Support for the conclusion: houses built with thick concrete walls cost less to heat and cool than wooden houses do. The concrete and wooden houses in the study were identical in every other significant way.

Initial thought after reading the FIB: We need to find a reason from the answer choices to back the author's conclusion, a strengthener.

Prethinking: How will the concrete house save more money in practice than it saved during the experiment ($55)?
Strengthener #1: a choice that somehow proves that concrete houses are, in practice, more efficient than the concrete houses in the researcher's experiment.
Strengthener #2: a choice that proves that wooden houses on average are less efficient than wooden houses in the experiment.

Keeping these 2 points in mind let's do answer choice analysis:

Choice A: This choice may seem attractive at first glance, but notice that the conditions claimed in this choice are true for both concrete houses and wooden houses, hence it doesn't provide us a contrast with the data in this choice. For instance, assume that in the experiment, concrete houses' energy bills on average comes to $200, and wooden houses' $255. So, if you are at most of the other places in the country, you can expect to see lesser dollar amount in bills than each respective type of house in the experiment. But will you see the margin between them "increase"?? Well now that would be an external assumption which is incorrect in the GMAT For another instance, the relationship between the margin (the $55 saving per month) and the net energy bill might be DIRECTLY proportional due to the material science properties of concrete and wood at extreme temperatures, so when you live in places with further extreme temperatures (cooler and hotter) from the average you can expect to see HIGHER savings. BUT, as you come to the cities with lesser deviation from the normal or average temperature, you will see your margin decreasing this would rather weaken the author's claim. INCORRECT CHOICE.

Choice C: By indicating that the insulation in wooden houses is usually worse than in the high-quality wooden houses in the experiment, we would back the author's claim that using concrete houses in practice will save people more than the $55 because the wooden houses in the experiment were of higher quality and consumed lesser energy than a typical wooden house, hence, deflating the savings in the experiment. Btw, this aligns too well with strengthener #2. CORRECT.

Choice D: This choice same as choice A, but in a more blunt way, assumes external info that the thickness of walls in the concrete houses on average is lesser than the concrete houses in the experiment. INCORRECT.

Hope this helps science guys looking for numeric explanations.­

MartyMurray , Requesting a more detailed explanation for option D and option A. Thank you in advance !!

Posted from my mobile device

­Which of the following most logically completes the passage? 

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 ________. 

The passage presents some comparative information about the cost of heating houses built with concrete walls and that of heating wooden houses.

It then states a conclusion:

In practice, most people choosing a concrete house over a wooden one would probably realize still greater monthly savings on energy

We can tell that that statement is a conclusion by noticing that it's followed by "because __________."

In this type of context, "because" is an evidence marker, and what follows "because" is a premise that supports the conclusion that precedes "because."

So, the choice that fills the blank must be a premise that supports the conclusion, "In practice, most people choosing a concrete house over a wooden one would probably realize still greater monthly savings on energy."

A - 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 choice provides support for the wrong conclusion.

The conclusion we need to support involves people saving on energy because of having a concrete house rather than a wooden house. On the other hand, this choice indicates that people would simply spend less on energy, on average, regardless of what type of house they have.

After all, if this choice is true, then, on average, people would likely spend less in winter and summer to heat and cool their houses respectively than was spent to heat and cool the houses in the survey. After all, given what this choice says, average outdoor temperatures are less extreme than the outdoor temperatures in the region where the houses in the survey were located, and it costs less to heat and cool a house when outdoor temperatures are less extreme.

At the same time, the differences in temperature mentioned by this choice would not cause people who have concrete houses to save more. Spending less because of less extreme outdoor temperatures is not the same as saving because of having a concrete house. In fact, being in a region where outdoor temperatures are less extreme would allow people who have wooden houses to spend less as well.

Eliminate.

B - 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 

If antyhing, this choice casts doubt on, rather than supports the conclusion.

After all, if this choice is true, then the houses in the survey are similar to average houses. The fact that they are similar in this way indicates that the savings achieved by people in average houses would be about the same as, rather than greater than, the savings achieved in the case of the concrete house in the survey.

Eliminate.

C - 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 choice is interesting.

If this choice is true, then the wooden house in the survey was better insulated than the average wooden house. Of course, in that case, having that concrete house rather than the wooden house in the survey resulted in less-than-average savings because the difference between the insulating properties of the concrete and the wood in those houses was less than average.

So, if this choice is true, the average person would save more than was saved in the case of the survey houses by having a concrete house rather than a wooden house because, normally, the difference between wood and concrete is greater.

So, this choice supports the conclusion.

Keep.

D - 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

This choice would support the conclusion if the passage said that the concrete house in the survey had relatively thin walls. After all, in that case, people whose houses have average, rather than relatively thin, concrete walls would save even more by having concrete walls rather than wooden walls.

At the same time, the passage doesn't say that the house in the survey had relatively thin concrete walls. So, for all we know, it had average concrete walls. In that case, the fact that relatively thin concrete walls provide only slightly greater energy efficiency than wooden walls is irrelevant. After all, in that case, there's no reason to believe that the average house with concrete walls has thicker walls than the concrete house in the survey.

Eliminate.

E - 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

The conclusion that the correct answer must support is about energy costs, not maintenance costs or total costs. So, because maintenance costs have no clear effect on energy costs, this information about maintenance costs has no bearing on the conclusion.

Eliminate.

Correct answer: C­