Logical reasoning PrepTest 110 · Section 2 · Question 2

Incorrect. The premises already establish that this is the case. The gap in the logic is between this valid conclusion and the actual one stated in the stimulus—that the city should invest in new subway cars.

Incorrect. There's no discussion in the stimulus of "[c]ost—effective" subway cars so this answer is out of scope.

Incorrect. Relative economic sense ("better") is out of scope since the premises are all about something making good (not better) economic sense.

Incorrect. This answer might serve as a necessary premise, but it doesn't mean it's a sufficient one. Even if they're affordable, they may not be worth investing in if they don't factor into making the subway system efficient and attractive.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Good economic sense → City should do it
Efficient, attractive subway system — Good economic sense
Therefore — The city should purchase new subway cars

Answer Anticipation:
The conclusion makes a recommendation as to what the city "should" do—buy new subway cars. There is a premise in the stimulus that establishes a sufficient condition guaranteeing the city should do something—if it makes good economic sense then the city should do it.

And the premises do establish that an efficient attractive subway system makes good economic sense. However it never establishes that purchasing new subway cars is necessary to having such a subway system. Maybe the tracks the stations or the operating system can be upgraded instead.

This answer attempts to apply a conditional to a specific case but it doesn't establish that the specific case meets the sufficient condition. Let's find an answer that connects subway cars to the efficient attractive system.

Answer Explanation:
This answer connects the new cars to the efficient attractive subway system. Since such a system makes good economic sense and the city should do things that make good economic sense this answer guarantees that the city should buy these new cars.

Key Takeaway:
A common pattern in Strengthen with Sufficient Premise questions will attempt to apply a conditional to a specific case but fail to show that the case meets the sufficient condition. When that happens find the answer that connects the details of that case to the conditional trigger.