Q16 - Engineer: Thermophotovoltaic generators are devices

[mshinners]

What does the Question Stem tell us?
This question is asking for a necessary assumption.

Break down the Stimulus:
"The engineer presents two facts:

1. TPV generators convert heat into electricity (you're not spending time trying to pronounce thermophotovoltaic, are you?).
2. manufacturing steel produces huge amounts of wasted heat.

From these facts the engineer concludes that, if steel plants could feed wasted heat into TPV generators, they would greatly reduce their electric bills This is an intermediate conclusion that supports the engineer's final conclusion: feeding the heat into TPV generators would allow the plants to save money."

Any prephrase?
"There are two possible gaps in logic here. Do we know that the TPV generators produce enough electricity to ""greatly"" reduce the electric bills? Even if they do, will this allow the plants to save money? Does it cost anything to feed waste energy into the TPV generators?

We don't need to be engineers to answer LSAT questions. If you're thinking, ""I don't know anything about thermophotowhatever generators,"" that's the point! You shouldn't have to. This is a logic problem, not an engineering problem. The engineer should present all the facts we need to accept his conclusion."

Answer choice analysis:
A) If the plants will save money by using these generators, you might argue that they would have to be "cost effective." However, they don't have to be more cost effective than any other method.

B) This sounds really good at first, but notice that the stimulus is about what would happen if plants could feed the waste heat into the generators. We don't have to assume that they currently can.

C) Correct! This addresses the second gap we found. If purchasing and installing the generators would cost more than the plants would save by using them, they won't be saving money.

D) For the intermediate conclusion to be true, we need to assume that some plants use electricity. Otherwise, it would not be possible to reduce their electric bills. However, we don't need to assume that electricity is the primary source of energy.

E) This reverses the conditional logic of the intermediate conclusion. It tells us that if some plants could greatly reduce their electricity bills, then they must use some method of converting waste energy into electricity. This isn't something we have to assume. There could be other ways for plants to reduce electricity bills without that having any impact on this argument.

Takeaway/Pattern: Notice when an argument contains an intermediate conclusion. The correct answer will often involve the gap in logic between the intermediate conclusion and final conclusion, as in this case, but any gap between the initial premise and the intermediate conclusion is also fair game.

#officialexplanation

[imasexybastard]

Why is B wrong. I understand why C is correct--justifies the "thereby saving money"--but I don't see why B isn't a necessary assumption as well.

[gotomedschool]

I think you answered your own question--although, I'll give you my justification with a disclaimer because I'm not 100% sure about this.

The conclusion is that if steel plants could feed heat to the generators, they would greatly reduice their electrib bills, thereby saving money.

C is correct because it is necessary to the argument that the amount of savings on their electric bills would indeed save them enough money by greatly reducing their electric bills. Basically if this wasn't true the argument would be destroyed.

I found B to be incorrect, although it was VERY TEMPTING, because it doesn't tackle the issue at hand--which is saving on electric bills. Even if B was true and they could convert SOME of that heat into electricity, that doesn't justify the conclusion that they would greatly reduce their electric bills, thereby saving money. Maybe the amount of heat they are able to convert to energy saves them 1/1000000000000th of the cost of their electricity bill/the technology.

[imasexybastard]

I think you answered your own question--although, I'll give you my justification with a disclaimer because I'm not 100% sure about this.

The conclusion is that if steel plants could feed heat to the generators, they would greatly reduice their electrib bills, thereby saving money.

C is correct because it is necessary to the argument that the amount of savings on their electric bills would indeed save them enough money by greatly reducing their electric bills. Basically if this wasn't true the argument would be destroyed.

I found B to be incorrect, although it was VERY TEMPTING, because it doesn't tackle the issue at hand--which is saving on electric bills. Even if B was true and they could convert SOME of that heat into electricity, that doesn't justify the conclusion that they would greatly reduce their electric bills, thereby saving money. Maybe the amount of heat they are able to convert to energy saves them 1/1000000000000th of the cost of their electricity bill/the technology.

Thanks for the explanation, but I'm still a little confused. Even if the main issue is saving on electric bills, isn't a necessary assumption that it's actually possible to convert the at least some of the heat into electricity. Using the denial test, wouldn't "using current tech, it would be IMpossible...convert at least some of that heat into electricity" hurt the argument--if they can't convert the heat into electricity, how are they supposed to save money?

Is it wrong b/c the conclusion argument already assumes that it's possible to convert heat into electricity--from the premise and the "if" in the conclusion?

[dina]

I ruled out B because the engineer's argument is "IF steel manufacturing plants could feed the heat they produce into thermophotovoltaic generators, they would greatly reduce their electric bills."

Therefore, he is NOT assuming that they currently can. He is saying if that is possible (even if it is not currently but only in the future), there would be savings.

hope that helps!

[bbirdwell]

That's exactly right -- the possibility is built into the argument, and we need not assume anything about "current" tech because the engineer is speculating about the future.

[hwsitgoing]

Hi,

I'm just wondering why D is incorrect. If the plants don't use electricity as their source of energy wouldn't the whole argument be destroyed?

Thanks!

[bbirdwell]

You're right in theory, but the negation of (D) is not that the plants "don't use electricity." The negation of (D) is that electricity is not the PRIMARY energy source, in which case the argument still stands (they can save money on their bill). In other words, it's not necessary that electricity be the primary source.

Words like "primary" are red flags. They're not always wrong, but scrutinize them carefully!

[sukim764]

This was a tough question for me primarily because of the latter portion of the answer choice C: sufficient to cover the cost of purchasing and installing those generators."

When I initially saw this choice, I thought to myself, why would that be necessary? What does the initial cost of purchasing and installing these machines have to do with reducing a company's electricity bills? For example, the cost to install the machine is $1,000 and a company pays $500 a month for electricity. If they were to install the machine, their bill would drop to $250. This was sort of why I eliminated this answer.

But upon reading your guys' responses, I see that it is necessary, EVEN IF the savings from the new bill don't compensate for the initial cost immediately. Over time, it must be sufficient in order to 'save money.'

Please feel free to chime in if there's anything that I've overlooked or if there's a simpler way of seeing this problem.

Thanks!

[nlschultheis]

I had initially chosen B as my answer choice and I now understand why that is incorrect with the engineer leaving the option open using the soft language in the stimulus, however, I am still unsure of C.

Why does "saving money" have to constitute a total net gain of money. even if the installation cost more, the company is still spending less on each electric bill and is therefore "saving" money they would otherwise be spending on the electric bill.

Therefore, the company can still be "saving money" on each electrical bill even if it spent more money overall to install?

[ManhattanPrepLSAT1]

Why does "saving money" have to constitute a total net gain of money. even if the installation cost more, the company is still spending less on each electric bill and is therefore "saving" money they would otherwise be spending on the electric bill.

I can't agree with that. This feels a lot like some of the advertisements we see on tv. They say, "buy this $1200 flat-screen television and save $400." I always wonder at that point. How is this saving me money, if I'm spending money I wouldn't have spent otherwise?

Lets look at the last sentence very carefully. It distinguishes between two ideas: reducing the electric bill and saving money. Since the argument distinguishes between them, I think it's fair to distinguish them in our evaluation of the argument.

If the steel-manufacturing plant spends more on the purchase and installation of the thermophotovoltaic generators than it recovers through a reduction in their electric bills, the steel-manufacturing plant has not "saved" any money.

Although I like your creative thinking nlschultheis!

[logicfiend]

I ruled out B because the engineer's argument is "IF steel manufacturing plants could feed the heat they produce into thermophotovoltaic generators, they would greatly reduce their electric bills."

Therefore, he is NOT assuming that they currently can. He is saying if that is possible (even if it is not currently but only in the future), there would be savings.

hope that helps!

This is so important and it's used as a reoccurring trap answer in other flaw and necessary condition questions. Watch out for it!

[jm.kahn]

Why does "saving money" have to constitute a total net gain of money. even if the installation cost more, the company is still spending less on each electric bill and is therefore "saving" money they would otherwise be spending on the electric bill.

I can't agree with that. This feels a lot like some of the advertisements we see on tv. They say, "buy this $1200 flat-screen television and save $400." I always wonder at that point. How is this saving me money, if I'm spending money I wouldn't have spent otherwise?

Lets look at the last sentence very carefully. It distinguishes between two ideas: reducing the electric bill and saving money. Since the argument distinguishes between them, I think it's fair to distinguish them in our evaluation of the argument.

If the steel-manufacturing plant spends more on the purchase and installation of the thermophotovoltaic generators than it recovers through a reduction in their electric bills, the steel-manufacturing plant has not "saved" any money.

Although I like your creative thinking nlschultheis!

I was very confused by this question especially because in PT-60.LR1.15, the LSAT test makers had used "saving money" to mean not the total net gain of money.
https://www.manhattanprep.com/lsat/foru ... t1844.html

In that question had "saving money" total net gain of money, choice A in 60.LR1.15 would also be a necessary assumption due to similar reason as C is for this question.

I ruled out C only because I had encountered 60.LR1.Q15 before and there LSAT test makers didn't mean saving money to assume that there is a net saving after one has accounted for the cost of installation of water faucets.

Can experts please help with resolving this discrepancy between the credited choices in 60.LR1.Q15 and this question?

[luluc]

I was very confused by this question especially because in PT-60.LR1.15, the LSAT test makers had used "saving money" to mean not the total net gain of money.
https://www.manhattanprep.com/lsat/foru ... t1844.html

In that question had "saving money" total net gain of money, choice A in 60.LR1.15 would also be a necessary assumption due to similar reason as C is for this question.

I ruled out C only because I had encountered 60.LR1.Q15 before and there LSAT test makers didn't mean saving money to assume that there is a net saving after one has accounted for the cost of installation of water faucets.

Can experts please help with resolving this discrepancy between the credited choices in 60.LR1.Q15 and this question?

First, "saving money" should always mean net gain of money unless it is qualified with "saving money in a specific way/area."

PT60,I,Q15 and PT 61,II,Q16 do not demonstrate inconsistencies in using "saving money" because the contexts where they were used and the questions asked are different. It seems like you did not really understand PT60,I,Q15.

For Q15, we are asked to find flaw in Rebecca's reasoning. Her reasoning is:
P: I have had lower water bill since I installed a water-saving faucet.
C: It is not true that the manufacturers' claims are exaggerated.
What's the gap? The premise of "lower water bill" does not support her conclusion of "manufacturers' claims are not exaggerated" because the manufacturer does not only claim that she will get lower water bill. Instead, the manufacturer probably claimed a specific amount money that will be saved. We know this because Camille said "manufacturers of water-saving faucets exaggerate the amount of money such faucets can save." Rebecca assumes "lower water bills" is "fulfilling the manufacturer's claim" while it could be the case that the amount of money she saved in water bill falls well short of the amount of saving that manufacturers claim.

(A) is incorrect not because cost of installing is irrelevant to her overall savings; this whole issue of comparing cost of installing with overall saving is simply not what she takes for granted. Her conclusion is comparing what she has saved with the manufacturer's claims and not about her overall savings. If the conclusion were "thus, I have saved money " or "thus, it is not true that the manufacturers' claim that we will save money is wrong," (A) would be a correct answer.

In other words, (A) is irrelevant to Rebecca's argument because we do not know what the manufacturer's claim is. Maybe it is a claim about overall saving or maybe it is a claim about saving on water bills per cycle. Either way, Rebecca's argument is vulnerable because she assumed she saved as much as the manufacturer claimed.

I am not an expert and replied because your question has been up for a long time. Hope this helps and if not, maybe an expert can help you see the issue more clearly.

[dhlim3]

To make this easier for everyone, we can break down the argument this way:

Premise: If steel-manufacturing plants could feed the heat they produce into thermophotovoltaic generators, they would greatly reduce their electric bills.

Conclusion: Therefore, if implemented, the plant will save money."

When you look at it this way, it becomes much more clear that the missing link is between the reduction of the electric bill and saving money. The whole part about heat conversion to electricity becomes irrelevant because it is assumed to be true as stated on the premise. When looking at the answer choices, C is the only one that brings forth the missing link.

[tuesdayninja]

Quick hypothetical, if the conclusion was instead 'If steel-manufacturing plants feed the heat they produce into TPV generators, they would greatly reduce their electric bills, thereby saving money", would B be a necessary assumption then? Or would answer B have to drop 'Using current technology' to be correct in that case?

[ManhattanPrepLSAT1]

Quick hypothetical, if the conclusion was instead 'If steel-manufacturing plants feed the heat they produce into TPV generators, they would greatly reduce their electric bills, thereby saving money", would B be a necessary assumption then? Or would answer B have to drop 'Using current technology' to be correct in that case?

I think what you did is took out the word "could" from the conclusion and made the conclusion more "if they do this, then that will happen." And if the argument concluded that "that will happen," it would need to assume that "this occurs." This removes the issue of whether the technology currently exists. The answer is no, this would not fix the difference between the gap in the argument and answer choice (B). The reason is that the conclusion is conditional. It's "if this, then that." The argument doesn't actually say that the steel producers will save money, but rather, if they feed the heat into generators, then they would save money.

If a conclusion is conditional, then the argument doesn't assume that the "if" part is true.

Hope that helps!

[andrewgong01]

I wanted to check my understanding for "B" because my rationale for eliminating it, unlike the previous posts, did not even consider the conditional wording in the stimulus. To be honest, I don't even think I took that into account when going through the answer choices or I was too convinced with "C" to dig deeper

I ruled out "B" because I thought during the preptest it was a premise booster that just tells us this could happen for real ( we can produce electricity through heat) but the reason why it is wrong is because it does not link us to either of the conclusions.

First, it does not bridge the gap to say that conversion of energy through this generator leads to lower electric bills (Does it really lower electric bills? What if this generator uses just as much electricity or requires the factory to operate 24/7 so the factory is now opened longer to? )

Second, it does not bridge the gap directly to the conclusion either on saving money (How much is this new generator?)

In other words, I didn't see "B" problem as the fact that it was being fitted into the argument where the argument told us it was a hypothetical (and hence we do not need to assume the hypothetical is true or will occur); rather, I saw it as that "B" was boosting a Premise and not bridging the gap to either saving money or lower electricity bills

[ohthatpatrick]

The way you're judging it, it sounds like you're thinking more in terms of Sufficient Assumption. Some of the same instincts obviously overlap a ton in Necessary Assumption, but you don't want to knock an answer because it FAILED to do something it SHOULD have done.

With Necessary Assumption (and Inference), it's not always the best or most interesting assumption/takeaway that gets rewarded in the correct answer.

There can be many assumptions the argument is making / many possible inferences that could be drawn. Sometimes we prephrase one or two possible answers and it makes it hard to flexibly consider a different idea.

It's somewhat fair to call this a Premise Booster, although I'm not a huge fan of that term. No answer choices actually tell us something we've already heard about.

If they're adding extra texture / detail to something we heard about in the premise, we're just saying, "cool, but the author doesn't NEED that extra texture/detail for his argument to work".

We heard that thermophotovoltaic generators can convert heat into electricity, but we never heard that using current technology we could feed heat from a steel-plant INTO one of those generators.

So you'd still be asking yourself, "Does the author NEED to believe that current technology allows us to feed heat from a steel-plant into a generator?"

And the answer, "No", is still based on the fact that the author's conclusion is not committing itself to what's possible 'using current technology'.

[MollyO658]

I eliminated C at first because I thought "purchasing and installing those generators" was out of scope, but I think the negation technique can be helpful here. If the amount of money they'd save on electric bills by using the generators was NOT sufficient to cover the cost of purchasing/installing them, then the plant wouldn't necessarily be saving money. So in order to conclude that using the generators leads to reduced electric bills/saving money, we have to assume that the generators aren't costing them in some other way (i.e., purchasing/installing).

Can someone confirm if this line of reasoning is correct??