GMAT Critical Reasoning: Sample Weaken Question

Written by Kelly Granson. Posted in GMAT Sample Questions

gmat critical reasoningIn this entry, we are going to examine how knowing the difference between necessary and sufficient conditions can help you weaken the conclusion of an argument. Consider the following example.

Expert: In an effort to minimize its electricity bills, UniCorp equipped the lighting system on its premises with detectors that automatically turn the lights off when no one is present in the building. This measure, however, did not lead to any significant reduction in the amount of electricity used by UniCorp. Since reducing the work hours of the employees is out of the question, it is unlikely that the company will succeed in its attempts to save on electricity.

Which of the following, if true, would most significantly weaken the expert's prediction?

A. UniCorp could reconsider its policy concerning the length of the employees' working hours.

B. UniCorp is about to implement a plan to optimize the use of laptops and other electrical devices by all employees.

C. Other companies of the same size have significantly larger electricity bills than does UniCorp.

D. UniCorp is planning to lay off some of its staff in the near future.

E. UniCorp has made a decision to uninstall the new detection system.

The expert makes the following case. The company wants to cut down on its electricity consumption. The lights now automatically go off when the building is empty. This measure had little effect, so apparently the problem was not connected with employees forgetting to turn the lights off upon leaving the building. The expert concludes that if this measure has failed, UniCorp simply won't ever get smaller electricity bills. He views using less electricity for lighting as a necessary condition for reducing total consumption and thinks that if that is not sufficient, nothing else will be. What the expert does not take into account is that some other measures might be sufficient to reduce the amount of electricity used by the company. Let's look for an answer that shows how UniCorp could still save energy even if the new system is not very helpful.

Choice A attempts to deny one of the premises. The expert's claim that the company is not going to reduce the working hours is not part of the conclusion; therefore, we should not argue with it but treat it as a fact.

Choice B is correct. It informs us about another measure that may very well be sufficient to achieve the desired result.

Choice C attempts to prove that UniCorp already uses minimal electricity (and thus shouldn't be so concerned with reducing that amount). This claim, however, has no influence on our conclusion—regardless of whether UniCorp should want to reduce the amount of electricity it consumes, the conclusion remains that if it failed to do so with the help of the new lighting system, it will fail in the future.

Choice D does somewhat weaken the conclusion, since fewer employees could conceivably result in lower electricity consumption, but the word some here is ambiguous—maybe the lay-off will be so small that it will have no significant effect. B is a much stronger "weakener" in this case.

Choice E is not in any way connected with the conclusion of the argument. Although the new system proved to have little effect, it certainly does not prevent UniCorp from saving electricity, so even if it is uninstalled, the company will still fail to use less electricity than it does now.

In this question, we weakened the conclusion of the argument by showing that the condition the author views as necessary is not the only possible measure to bring the desired result. If you want to cast doubt on the conclusion of an argument where the author deems a certain condition sufficient, look for an answer proving that it is not enough. Being able to spot those necessary or sufficient conditions assumed by the author can make weaken questions much easier to handle.


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