Critical Reasoning

Citizens of Parktown are worried by the increased frequency of serious crimes committed by local teenagers. In response, the city government has instituted a series of measures designed to keep teenagers at home in the late evening. Even if the measures succeed in keeping teenagers at home, however, they are unlikely to affect the problem that concerns citizens, since most crimes committed by local teenagers take place between 3 pm and 6 pm.

Which of the following, if true, most substantially weakens the argument?

a) Similar measures adopted in other places have failed to reduce the number of teenagers on the streets in the late evening.

b) The crimes committed by teenagers in the afternoon are mostly small thefts and inconsequential vandalism.

c) Teenagers are much less likely to commit serious crimes when they are at home than when they are not at home.

d) Any decrease in the need for police patrols in the late evening would not mean that there could be more intensive patrolling in the afternoon.

e) The schools in Parktwon have introduced a number of after-school programs that will be available to teenagers until 6 pm on weekday afternoons.

Rastis wrote:Citizens of Parktown are worried by the increased frequency of serious crimes committed by local teenagers. In response, the city government has instituted a series of measures designed to keep teenagers at home in the late evening. Even if the measures succeed in keeping teenagers at home, however, they are unlikely to affect the problem that concerns citizens, since most crimes committed by local teenagers take place between 3 pm and 6 pm.

Which of the following, if true, most substantially weakens the argument?

a) Similar measures adopted in other places have failed to reduce the number of teenagers on the streets in the late evening.

b) The crimes committed by teenagers in the afternoon are mostly small thefts and inconsequential vandalism.

c) Teenagers are much less likely to commit serious crimes when they are at home than when they are not at home.

d) Any decrease in the need for police patrols in the late evening would not mean that there could be more intensive patrolling in the afternoon.

e) The schools in Parktwon have introduced a number of after-school programs that will be available to teenagers until 6 pm on weekday afternoons.

Premise: The city government has instituted measures to keep teenagers at home in the late evening, but MOST CRIMES committed by teenagers take place between 3pm and 6pm.
Conclusion: The new measures are unlikely to curb the increase in SERIOUS CRIMES.

Notice the change in LANGUAGE and SCOPE.
The premise is about MOST CRIMES, but the conclusion is about SERIOUS CRIMES.
MOST CRIMES ≠ SERIOUS CRIMES.
The assumption here is that the CRIMES committed between 3pm and 6pm are SERIOUS.
To break the link between the premise and the conclusion, the correct answer must show that the CRIMES committed between 3pm and 6pm are NOT SERIOUS.

Answer choice B does just that: Crimes committed by teenagers in the afternoon are mostly small thefts and inconsequential vandalism.

The correct answer is B.

But isn't that answer actually strengthening the conclusion? The conclusion you state is that the curbing of serious crimes won't happen. Answer choice B would actually strengthen that. If we're talking about weakening the PLAN, then answer choice B would work.

Rastis wrote:But isn't that answer actually strengthening the conclusion? The conclusion you state is that the curbing of serious crimes won't happen. Answer choice B would actually strengthen that. If we're talking about weakening the PLAN, then answer choice B would work.

The conclusion is that the plan (keeping teenagers at home in the late evening) is UNLIKELY to affect the problem that concerns citizens (the commission of serious crimes).
To weaken this conclusion, the correct answer must show that the plan WILL affect the problem that concerns citizens: that keeping teenagers at home in the late evening WILL lead to a decrease in the commission of serious crimes.
B states that only non-serious crimes are committed in the afternoon, implying that serious crimes are committed only at night.
Thus, keeping teenagers at home in the late evening WILL lead to a decrease in the commission of serious crimes, WEAKENING the conclusion that the plan is UNLIKELY to affect the problem that concerns citizens.

@GMATGuruNY

When you say that "B states that only non-serious crimes are committed in the afternoon, implying that serious crimes are committed only at night. "

Why are you assuming that no crimes are happening at daytime and the serious crimes happen at night time?

shantanuchandra wrote:@GMATGuruNY

Why are you assuming that no crimes are happening at daytime

The argument concludes that the frequency of SERIOUS crimes will not be reduced.
To support this conclusion, the passage cites the following premise:
Most crimes committed by local teenagers take place between 3 pm and 6 pm.
According to the OA, crimes committed in the afternoon are mostly SMALL and INCONSEQUENTIAL.
Since crimes committed between 3 and 6pm are SMALL and INCONSEQUENTIAL, they cannot be cited as evidence that the frequency of SERIOUS crimes will not be reduced.
Thus, the conclusion of the passage is weakened.