Logical reasoning PrepTest 152 · Section 2 · Question 7

Incorrect. The relative amount of money spent on natural gas compared to other expenses is out of scope of the argument since the conditional deals just with the cost of natural gas in the two towns.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Natural gas cost in Chester is more than 2x Tilsen → ChesChem moves to Tilsen
Currently, natural gas cost in Chester is 2x Tilsen
If natural gas in Chester goes up at all, then ChesChem will move to Tilsen

Answer Anticipation:
Taking a look at this argument, it can very much seem valid on first glance—the argument seems to apply a conditional. However, we know that the argument is flawed since the question is asking us for an assumption necessary to the argument, so we should dive back in. And when an argument appears to apply a conditional in a valid manner, but we know it doesn't, there's a good chance that the premise establishing the sufficient condition doesn't actually meet that condition.

With that in mind, let's take a look at this one. Currently, natural gas in Chester is 2x the cost it is in Tilsen. Thinking about how we know this argument is flawed, how could an increase in the cost of natural gas in Chester not result in it being more than twice that of Tilsen? Well, the cost in Tilsen would also have to increase (by at least half of what it did in Chester). The argument requires assuming that this increase in Tilsen doesn't happen, so let's find that answer.

Answer Explanation:
This answer choice highlights the possibility that would prevent ChesChem from moving to Tilsen even if natural gas prices in Chester rise. If the price of natural gas in Tilsen does increase, then it could also increase in Chester without triggering a move based on the conditional rule.

Key Takeaway:
When an argument appears valid but you know it's not, dive into the feature of the argument that is most likely to be flawed. Here, after determining that the conditional logic flowed in the right direction, the next most likely flaw is a premise that doesn't actually establish the sufficient condition is met. Challenging the applicability of the premise to that sufficient condition can make it a lot easier to see the scenario that highlights how they're different, as we did here.

Incorrect. Profitability doesn't factor into the equation (i.e., the conditional rule or conclusion), so this answer is out of scope.

Incorrect. While cheaper gas prices are the only difference set up as a sufficient reason to move to Tilsen, that doesn't rule out the possibility that they'd also see other benefits after the move. It could be that natural gas prices are the only reason to take on the expense and difficulty of moving, but there are a bunch of smaller benefits from the move that wouldn't by themselves trigger the relocation.

Incorrect. The rule that would trigger a move is that the gas prices in Chester are more than double those in Tilsen. While that could happen from prices in Chester going up, it could also happen from prices in Tilsen going down. This answer, in ignoring the possibility of that price decrease, is not necessary for the argument.