#12 - Photovoltaic power plants produce electricity from sun

[PresidentLSAT]

Hello,

Can someone please help me with my line of reasoning. Just when I think I have sufficient assumption locked, a question comes along and contorts my entire understanding.

The argument concludes that PV PP are a cheaper source of electricity than conventional PP.

Premise: Technology has made the production of PV PP cheaper to the point that it's 10% of its cost 20 years ago, whereas the cost for conventional has increased.

So if the cost of PV PP is $10 ($100 in 2001), then conventional PP is $20 in 2021.

I still don't get it. How do I fit D in here?

I chose C because I thought if technology is what has reduced the cost of PV PP, then I have to rule out the possibility that the technological advancement that impacted PV PP cannot have the same price effect on conventional PP. How is this wrong?

D as an answer is confusing; 10x less-8%, 9%, or 11%, 22%.

Thanks in advance.

[Rachael Wilkenfeld]

Hi President,

I'm not sure where you are drawing the 20 dollars for traditional plants from, but we can use it as an example.

Let's say it was 100 dollars 10 years ago for PV . Now it's less 10 dollars.

For traditional plants, let's say it was 20 dollars 20 years ago, and now it's 30 dollars.

In order for us to KNOW that the traditional needs to cost more than the PV now, we need to somehow link into the first example---we need to know how traditional plants compare not to themselves in the past, but to the PV.

For answer choice (D), it tells us that 20 years ago, the cost of PV energy was less than 10 times the cost of traditional Does that justify our conclusion that it's more expensive now? Well, if PV less than 10% of the cost it was in the past, that means that the past was more than 10 times the cost of it now. If the PV was less than the 10X the cost of traditional, than taking 10% of the PV number will be less than the traditional number. Answer choice (D) links the relationship between the PV plant cost and the traditional costs to draw the conclusion.

Now, it's not an assumption question, so I'm not going to do an assumption negation technique here. However, I do want to play around with numbers a bit to make the concept more clear.

Our correct answer says that 20 years ago, the PV cost was less than 10X the cost of traditional power. Let's look at what that 10X the cost could do.

1. 20 years ago, PV is more than 10X the cost of traditional power (not consistent with answer choice (D).
We could say that traditional power cost 10 dollars, PV cost 150. Now, PV could cost 14, while traditional could cost 11. That's consistent with the facts (PV is less than 10% of prior cost, traditional power increases). However, it is inconsistent with the conclusion drawn. Thus, an answer choice saying this would not justify our conclusion.

2. 20 years ago PV is less than 10X the cost of traditional power (this is answer choice (D).
20 years ago, traditional power could cost 11 dollars, and PV 100. PV now would cost less than 10, while traditional would be more than 11. This is why the answer choice justifies our conclusion. As long as that relationship holds, the PV will have to be less than the traditional in modern times.

Hope those examples help!

[PresidentLSAT]

Thank you!

The wording in choice D also played a role in my confusion-still does. Though this was tough to decipher, it cleared some concepts for me; in questions concluding cheaper rates and prices, look out for choices that compare them against each other.