Logical reasoning PrepTest 142 · Section 2 · Question 16

Incorrect. The conclusion is that using the heat with TPV generators would save money, not that it would save the most money or be the only way to save money. This answer is not necessary because other uses of heat saving more money doesn't undermine the argument about whether this use will save money.

Incorrect. This is a very tempting answer! However, note the conclusion of the argument—"So if steel-manufacturing plants can . . . " The argument doesn't assume that it's possible to use heat for TPV generators—it qualifies the conclusion as holding only if it can be done.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
TPV generators turn heat into electricity. Steel manufacturing makes heat. So if steel plants can use TPV generators, they'll reduce their electric bills and thus save money.

Answer Anticipation:
This argument ends with a quick jump that ends up making a huge difference to the logic of the argument.

The stimulus establishes that TPV generators can be used to convert heat to electricity. It can be assumed that steel-manufacturing plants use electricity in some way (they at least have lights), and the argument establishes that they generate a lot of heat. The conclusion qualifies itself by stating if it's possible for the plants to feed the heat into TPV generators, then the plants can save money on their electric bills.

There's a small jump there—maybe the operation of them takes more electricity than they generate—but there's a much bigger jump when it goes from this intermediate conclusion to the main conclusion. Even if we accept that the plants are saving money on their electric bills, that doesn't mean they'll save money overall—maybe there are other costs that would eat up more than the savings on electricity. If the plant is saving $100/mo on electricity, but it costs $1m for the generator, $1m to set it up, and $10k/mo to operate it, then that's a net loss.

The correct answer should, therefore, rule out another cost eating up all the savings from the decreased electric bill.

Answer Explanation:
The conclusion of the argument is that the plant would save money overall. Even if using heat to generate electricity lowers the electric bill, it might not save money if the other costs associated with the process outweigh the money saved. If the purchase and installation costs are higher than the money saved on the electric bill, then the argument falls apart.

Key Takeaway:
Whenever an argument's conclusion explicitly or implicitly includes an "overall" (here, it was implicit), the argument is likely ignoring factors that make up the overall. Start thinking about what the argument isn't considering and see how that plays into the logic.

Incorrect. Even if electricity isn't used in the steel-manufacturing process, a steel plant may still use electricity for other purposes—such as keeping the lights on or running computers used by certain workers.

Incorrect. This answer choice establishes using heat to generate electricity as necessary for some steel plants to save money on their electricity bill. The argument, however, doesn't require there to be plants that can save money only if they can use heat to generate electricity; it requires there to be plants that can save money if they can use heat to generate electricity.