GMAT Critical Reasoning: Weaken & Strengthen Strategy

The core of GMAT Verbal is Argumentation. Learn how to dismantle (Weaken) or fortify (Strengthen) an argument using our 3-step framework, applied to real exam questions ranging from Easy to Hard.

Defining the Objective

Before you look at the options, you must understand your goal. Both question types rely on the same logic, just in opposite directions.

Weaken The Argument	Strengthen The Argument
The Goal: Create doubt.	The Goal: Increase belief.
"What, if true, would make us question the conclusion?"	"What, if true, would make the conclusion more believable?"
Attack the Basis	Reinforce the Basis

The 3-Step Strategy for CR Success

1
Identify the ConclusionWhat is the author's final claim or recommendation? Re-read it if necessary.
2
Find the Basis (Premise)What reasoning led to that conclusion? What evidence forms the foundation?
3
Pre-Think the ImpactStrengthen: How can I reinforce the link between Basis and Conclusion?Weaken: How can I break the link between Basis and Conclusion?

Applying the Strategy

EASY LEVEL

Example 1: The Cocoa Argument (Weaken)

"Cocoa grown organically on trees within the shade of the rain forest canopy commands a premium price. However, acquiring and maintaining the certification that allows the crop to be sold as organically grown is very time-consuming and laborious. Meanwhile, the price premium for the grower is about 30 percent, whereas cocoa trees grown in full sun using standard techniques can have twice the yield of organic, shade-grown trees. Financially, therefore, standard techniques are the better choice for the farmer."

Step 1: Conclusion

Standard cocoa is better for the farmer financially versus organic cocoa.

Step 2: Basis

Standard has 2x yield. Organic has costs (certification) but only a 30% premium.

Step 3: Weaken Goal

Show that standard cocoa has hidden costs OR organic is still more profitable despite lower yield.

Question: Which of the following, if true, most seriously weakens the argument?

(a) Cocoa can be grown only in a climate that has the temperature and moisture characteristics of a tropical rain forest.
(b) Cocoa trees grown using standard techniques require costly applications of fertilizer and pesticides, unlike shade-grown trees.
(c) Although organically grown cocoa has long commanded a price premium over cocoa grown using standard techniques, its price has fluctuated considerably during that period.
(d) Cocoa is not the only cash crop that can be raised on plots that leave the rain forest canopy overhead esentially intact.
(e) Governments and international conservation organizations are working to streamline organic certification so as to relieve farmers of unnecessary work.

Why (B) is Correct:

This introduces a new cost factor for standard cocoa. Even if the yield is double, if the cost of fertilizers/pesticides is massive, the profit margin drops. This attacks the conclusion that "Standard is financially better."

MEDIUM LEVEL

Example 2: Traffic Enforcement (Strengthen)

"Budget constraints have made police officials consider reassigning a considerable number of officers from traffic enforcement to work on higher-priority serious crimes. Reducing traffic enforcement for this reason would be counterproductive, however, in light of the tendency of criminals to use cars when engaged in the commission of serious crimes. An officer stopping a car for a traffic violation can make a search that turns up evidence of serious crime."

Step 1: Conclusion

Reassigning police from traffic to serious crimes would be counterproductive.

Step 2: Basis

Traffic stops can lead to searching cars, which often uncovers evidence of serious crimes.

Step 3: Strengthen Goal

Show that traffic stops are indeed a highly effective way to catch serious criminals.

Question: Which of the following, if true, most strengthens the argument above?

(a) An officer who stops a car containing evidence of the commission of a serious crime risks a violent confrontation.
(b) When the public becomes aware that traffic enforcement has lessened, it typically becomes lax in obeying traffic rules.
(c) Those willing to break the law to commit serious crimes are often in committing such serious crimes unwilling to observe what they regard as the lesser constraints of traffic law.
(d) The offenders committing serious crimes who would be caught because of traffic violations are not the same group of individuals as those who would be caught if the arresting officers were reassigned.
(e) The great majority of persons who are stopped by officers for traffic violations are not guilty of any serious crimes.

Why (C) is Correct:

This connects the two groups. It says serious criminals are more likely to break traffic rules. This increases the probability that a traffic stop will catch a serious criminal, reinforcing the argument.

HARD LEVEL

Example 3: Lightning Hypothesis (Weaken)

"Typically during thunderstorms most lightning strikes carry a negative electric charge; only a few carry a positive charge. Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires. The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds."

Step 1: Conclusion

Extra positive strikes occur because of the presence of smoke particles.

Step 2: Basis

Correlation: Smoky areas have high positive strikes. Fact: Smoke carries positive particles.

Step 3: Weaken Goal

Delink the two. Show that the positive charge exists without the smoke, or due to another factor.

Question: Which of the following, if discovered to be true, most seriously undermines the hypothesis?

(a) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.
(b) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.
(c) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.
(d) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.
(e) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

Why (D) is Correct:

If the positive strikes continue weeks after the smoke particles have lost their charge, then the smoke particles cannot be the cause. This completely breaks the link.

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