Critical Reasoning

Photovoltaic power plants produce electricity from sunlight. As a result of astonishing recent technological advances, the cost of producing electric power at photovoltaic power plants, allowing for both construction and operating costs, is one-tenth of what it was 20 years ago, whereas the corresponding cost for traditional plants, which burn fossil fuels, has increased. Thus, photovoltaic power plants offer a less expensive approach to meeting demand for electricity than do traditional power plants.
The conclusion of the argument is properly drawn if which one of the following is assumed?
(A) The cost of producing electric power at traditional plants has increased over the past 20 years.
(B) Twenty years ago, traditional power plants were producing 10 times more electric power than were photovoltaic plants.
(C) None of the recent technological advances in producing electric power at photovoltaic plants can be applied to producing power at traditional plants.
(D) Twenty years ago, the cost of producing electric power at photovoltaic plants was less than 20 times the cost of producing power at traditional plants.
(E) The cost of producing electric power at photovoltaic plants is expected to decrease further, while the cost of producing power at traditional plants is not expected to decrease.
OA D

Good question....and I was wrong went for E

I have problem with OA D
According to this 20 yrs ago
Cost (n)< 20 Cost (T)
Today
new Cost(N')= 1/10 of cost (N)
Therefore
new Cost (N')< 2 Cost (T)

But then how it is economical

IMO E

Iam really wondering how D can fit in the bill!!!

Let us assume PVC(Photo-voltaic current) is 100 Rs/Hr today.So it means 20 years back it was 1000 Rs/Hr . Moreover Traditional Power Plant(TPP) will be certainly more than 100 Rs/hr as of today.Let us keep it as 100+X(X in Rs).

So in the forseeable future if the rate of growth PVC current cost is less than TPP current cost, then photovoltaic power plants offer a less expensive approach to meeting demand for electricity than do traditional power plants. This is wat option E exactly says.
In my opinion I vote E.

Please explain how D fits in this ??

Vikram, could u post the OE for that CR

imo E

D can not be right

gmatmachoman wrote:Vikram, could u post the OE for that CR

Hey I don't have the OE.It's just a set of questions with answer options.

Seems E wuld be a greater fit with the given explanations.

wat say??

arorag wrote:I have problem with OA D
According to this 20 yrs ago
Cost (n)< 20 Cost (T)
Today
new Cost(N')= 1/10 of cost (N)
Therefore
new Cost (N')< 2 Cost (T)

But then how it is economical

Hi,

I see it in this way:

Argument said:

(1) Cost_Today (Photovoltaic power)= 1/10 Cost_20YearsAgo (Photovoltaic power);

and

(2) Cost_Today (Traditional Plants) = 1,1 Cost_20YearsAgo (Traditional Plants)
(Because =>...whereas the corresponding cost for traditional plants, which burn fossil fuels, has increased...)

BUT:
is it supposed to Photovoltaic power less expensive than Traditional Plants? I dont think so! We need to have relationship between Costs Photovoltaic and Traditional plants, to compare properly, and only (D) have this relationship:

Cost_20YearsAgo (Photovoltaic power)< 20 * Cost_20YearsAgo (Traditional Plants)

and thus:

10 Cost_today(Photovoltaic power) <10/11 Cost_Today (Traditional Plants) (Make substitution)

=> Cost_today(Photovoltaic power) <1/11 Cost_Today (Traditional Plants)

Finally, We can say that Photovoltaic power is better than Traditional Plants!

Cheers!

This question is offering us a conclusion about NOW--that photovoltaic cells 'offer' the cheapest electricity, using the simple present. That knocks (E) out of contention; anything discussing what is EXPECTED to happen to the prices in the future is Out of Scope of the argument.

For (D), however, the math indeed doesn't work as written in the OP. If solar cells were once 19 times more expensive than fossil fuel 20 years ago, they will now cost 1.9 times more than that cost. If the cost of fossil fuel increased by 50%, to 1.5 times the original price, fossil fuels will still be cheaper. vikram_k51, what's the source of this problem? Could an error have been introduced?

https://gmatclub.com/forum/cr-lsat-77997.html



I'm stumped.......

Can anyone please explain why D is correct here i am very confused on this one...

Regards,
Phil

In my opinion the answer must be C.

IMO D can be correct but it would have limitation. Consider the following scenario.

20 years ago say the cost of producing 1 unit of electricity by photovoltaic cells be $100 and let the present cost of producing the same electricity from fossil fuel be $12

So the present cost of producing electricity from photo cells is $10(follows from argument) and it is cheaper than that from fossil fuel ($12, our assumption)
But for D to be true, the cost of producing electricity from fossil fuels 20 yrs ago should be >$5

If it were say $4, then the cost of producing electricity from photo cells ($100 which is our assumption) will not be less than 20 times of $4 ($80) and any value less than $5 will have the same fate.

The question doesn't state the extent of increase of cost of producing electricity from fossil fuels.

I am new to this and so please correct me if am wrong

Guys can anyone give a decent reason why D is not right