Past LSAT Explained/PrepTest 30
October 2001 Form 1LSS51
Section I Logical Reasoning
Section II Reading Comprehension
Question type: Semi-flaw
Argument: Premise- Because a runner's feet remain in contact with the ground for shorter period of time on a hard running surface than on a softer one. Conclusion- Running tracks with a hard surface allows you to run faster, under dry conditions.
You're looking for an answer that shows that the argument provided only partial evidence for the conclusion.
Correct answer (C): This answer choice tells us that hard tracks affect the posture of the runners which minimizes wind resistance. This shows that the time a runner's feet remains on the surface isn't the only reason why hard surfaces allows runners to run faster.
A) Incorrect, since the conclusion already stated 'under dry conditions', we're looking for something that would affect running speed on hard surfaces in dry conditions.
B) Incorrect, irrelevant to the argument since it's stating differences between runners, not the running surface.
D) Incorrect, tempting since it seems to give another reason for running speed variations, but remember, we're looking for something that explains why running speed varies between hard and soft surfaces. Also remember, we're not looking to disprove the original argument, we're looking for another explanation with which to prove the argument. If we go with this answer choice, then the argument would fall apart, since we would ask ourselves, 'would a soft surface track at high altitude allow runners run faster than a hard surface track at sea level?'
E) Incorrect, all this answer choice does is try to throw us off, does nothing to the argument.