Logical reasoning PrepTest 115 · Section 4 · Question 12

Incorrect. This answer doesn't distinguish between different heights of arch dams, so it can't explain the higher rate of collapse for the shorter ones.

Incorrect. This answer might explain why there may be fewer arch dams, but not why the shorter ones are collapsing more than the taller ones.

Correct. Argument or Facts:
Facts

Question Type:
Paradox

Stimulus Summary:
General rule - The higher the dam, the larger the forces that can cause a collapse
Arch dams - Despite many such dams over 100m high, all collapses have been of ones under 100m

Answer Anticipation:
As with all Paradox questions, let's start by clearly defining the paradox.

Here, there's a general relationship raised—the higher the dam, the large the forces pushing on it. Makes sense—a higher dam has more water behind it, after all! It then goes into details about arch dams, of which there are many that skew towards being over 100m tall. This might lead you to believe that those taller arch dams tend to collapse more, but the opposite is true—all collapsed arch dams were under 100m.

Since this Paradox question compares higher dams to shorter ones, especially among arch dams, we should anticipate an answer that brings up a point of comparison. In particular, since we're trying to explain an unexpected difference between the two heights of dams, we should expect another difference between them that can explain the differing collapse rates. Let's find an answer explaining why taller dams would be less prone to collapse despite the higher forces on them, or why lower dams are more prone despite less exposure to such forces.

Answer Explanation:
This answer brings up a difference between larger and smaller structures—and thus it applies to larger and smaller arch dams. If the larger dams are more carefully designed and constructed, they may be better able to withstand the forces they're subject to, even if those forces are larger. Since this brings up a relevant difference that can explain the higher collapse rate of the shorter dams, it's the correct answer.

Key Takeaway:
Paradox questions frequently deal with comparisons. If the paradox we're set to resolve has to do with unexpectedly different (or similar) outcomes, figure out if the resolution should bring up another relevant similarity or difference, and then find it!

Incorrect. This answer has nothing to do with different collapse rates between taller and shorter dams, so it doesn't resolve the paradox.

Incorrect. This answer doesn't relate the collapse rate of smaller arch dams to larger ones, which is what the paradox in the stimulus relates to, so this answer is out of scope.