Target Test Prep GMAT Verbal Challenge Question 7

Solution:

Breakdown of the argument:

Premise: Given the amount of sunlight in our area of the world, even if the roof of the average house in our area of the world were completely covered with solar panels, the panels would provide only about two-thirds of the electrical power used by the appliances a house typically has.

Conclusion: So, in our area of the world, rooftop solar will never be the sole source of electrical power for houses.

The answer choices to this question include some that support conclusions related to the conclusion of this argument. So, in order to avoid choosing one of those choices, we have to pay careful attention to the conclusion of the argument.

If we have a vague idea of the conclusion in our minds, such as “something about rooftop solar not being good,” we could choose one of the incorrect answers that seems to be something that one would have to assume to conclude “something about rooftop solar not being good. ”

On the other hand, if we are completely clear about what the conclusion is, we'll likely get this question correct.

CORRECT ANSWER(A) Electrically powered household appliances will not in general be redesigned to use around half the power that such appliances use today.

The energy analyst concludes that, in that area of the world, rooftop solar will never be the sole source of electrical power for houses. He bases that conclusion on the fact that, currently, even a roof full of solar panels generates only two-thirds of the power used by the appliances a house typically has.

Of course, in basing that conclusion on that evidence, he must be assuming what this choice says.

After all, if, contrary to what this choice says, electrically powered household appliances WILL in general be redesigned to use half the power that such appliances use today, then it's quite possible that, in the future, the average house will use only half the power it uses today.

In that case, it's quite possible that, since a roof full of solar panels can generate two-thirds of the power a house's appliances use today, and since two-thirds is significantly greater than half, rooftop solar will be able to provide plenty of power for the average house.

Of course, in that case, the energy analyst's argument falls apart, because, in that case, his evidence no longer supports his conclusion.

In that case, even though, currently, rooftop solar is unable to provide as much power as the average house uses, it would be possible that, in the future, rooftop solar will be the sole source of power for houses in that area of the world.

Thus, the energy analyst must be assuming that, as this choice says, appliances WILL NOT in general be redesigned to use half the power appliances use today.

(B) A household would not save money by generating two-thirds of the electrical power it uses by using rooftop solar panels.

This choice is tempting because it supports a conclusion related to the energy analyst's conclusion. This choice supports the conclusion that rooftop solar won't become widespread, or another similar conclusion.

Notice, however, that, in arriving at his conclusion, the energy analyst doesn't have to assume that a household would not save money by using rooftop solar.

After all, even if every household in that area of the world WOULD save loads of money by using rooftop solar to generate two-thirds of the energy the household uses, the fact that rooftop solar produces only about two-thirds of the power used by the appliances a house typically has would still support the conclusion that rooftop solar will not be the “sole source of electrical power” for households in that area of the world.

So, clearly, this choice does not state an assumption upon which the energy analyst's argument depends.

(C) People in the energy analyst's area of the world are not concerned about the effects on the environment of using fossil fuels to generate electricity.

This choice is tempting because it supports a conclusion related to the energy analyst's conclusion. This choice supports the conclusion that people in the energy analyst's area of the world won't be quick to adopt rooftop solar, or another similar conclusion.

Notice, however, that, in arriving at his conclusion, the energy analyst doesn't have to assume what this choice says.

After all, even if people in the energy analyst's area of the world WERE VERY concerned about the effects on the environment of using fossil fuels to generate electricity, the fact that rooftop solar produces only about two-thirds of the power used by the appliances a house typically has would still support the conclusion that rooftop solar will not be the “sole source of electrical power” for households in that area of the world.

So, clearly, this choice does not state an assumption upon which the energy analyst's argument depends.

(D) In the future, solar panels will generate much more power per unit of area than solar panels available today generate.

This choice is extremely tempting. It sounds so relevant to the argument. After all, the argument is based on how much power rooftop solar produces, and this choice is about a change in how much power rooftop solar can produce.

There's just one problem. This choice goes in completely the wrong direction. This choice weakens the energy analyst's argument.

After all, if what this choice says is true, then even though, currently, in the energy analyst's area of the world, rooftop solar generates less power than a household's appliances use, in the future, rooftop solar will generate much more power and, thus, might be able to generate all of the power that a household's appliances use.

Of course, in that case, it's possible that, in that area of the world, rooftop solar will someday be the sole source of electrical power for houses.

So, this choice is a weakener that destroys the energy analyst's argument.

(E) A roof covered with solar panels is not as attractive as a roof without solar panels.

This choice could be tempting if we are not clear about the conclusion of the argument. If we have a vague idea that the conclusion is “something about rooftop solar not being good,” then we might perceive this choice to be an assumption made by the energy analyst.

Notice however that, in arriving at his conclusion, the energy analyst doesn't have to assume what this choice says.

After all, even if, contrary to what this choice says, a roof covered with solar panels were the most attractive roof ever, the fact that rooftop solar produces only about two-thirds of the power used by the appliances a house typically has would still support the conclusion that rooftop solar will not be the “sole source of electrical power” for households in that area of the world.

So, clearly, this choice does not state an assumption upon which the energy analyst's argument depends.