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Difficulty: HardMost Strongly Supported Questions

Recent studies on urban noise pollution have demonstrated that in metropolitan areas, prolonged exposure to traffic noise exceeding 70 decibels significantly correlates with an increased incidence of stress-related cardiovascular conditions. However, the installation of acoustic barriers along major highways only reduces noise levels by an average of 5 decibels. Furthermore, in districts where speed limits were reduced from 50 mph to 30 mph, average traffic noise dropped by over 12 decibels. Curiously, the districts that implemented both acoustic barriers and speed limit reductions experienced no greater decrease in average traffic noise than those that only reduced speed limits.

Which one of the following is most strongly supported by the information above?

  1. A
    Decreasing traffic speeds from 50 mph to 30 mph is the most effective way for a metropolitan district to reduce the incidence of stress-related cardiovascular conditions.
  2. B
    If a metropolitan district has an increased incidence of stress-related cardiovascular conditions, its average traffic noise must exceed 70 decibels.
  3. The noise reduction effects of acoustic barriers and speed limit reductions are not entirely cumulative when both are implemented in a district.Answer
  4. D
    Metropolitan districts that maintain traffic noise levels at or below 70 decibels will not experience an increased incidence of stress-related cardiovascular conditions.
  5. E
    Acoustic barriers are incapable of reducing traffic noise by more than 5 decibels under any circumstances.

Answer

The noise reduction effects of acoustic barriers and speed limit reductions are not entirely cumulative when both are implemented in a district.
The stimulus establishes that speed limit reductions alone decrease noise by over 12 decibels, while combining them with acoustic barriers yields no greater decrease than the speed limit reduction alone. If the effects were fully cumulative, the combined reduction would be expected to be over 17 decibels. Because this does not occur, it is strongly supported that their individual noise reduction benefits do not fully add up when implemented together.

Step-by-Step Solution

1
Analyze the individual effects of each noise reduction intervention.
Acoustic barriers yield an average 5 decibel reduction; reducing speed limits yields a greater than 12 decibel reduction.
Establishing the baseline effectiveness of each method is necessary to evaluate what happens when they are combined.
2
Examine the outcome when both interventions are implemented simultaneously.
Districts using both methods saw no greater noise decrease than those using only the speed limit reduction (i.e., a drop of over 12 decibels).
This comparative data point is the key premise that must be reconciled with the individual reduction numbers.
3
Synthesize the findings to derive a logically proven statement.
Because the combined effect (roughly 12+ decibels) is less than the sum of their individual effects (roughly 17+ decibels), the benefits are not fully additive.
A 'Most Strongly Supported' answer must be a direct mathematical or logical consequence of the provided premises.

Key Concept

Synthesizing premise information to identify an unstated but logically required outcome regarding overlapping variables.
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