#15 - A certain experimental fungicide causes no harm to

[Administrator]

Complete Question Explanation

Assumption. The correct answer choice is (E).

Answer choice (A):

Answer choice (B):

Answer choice (C):

Answer choice (D):

Answer choice (E): This is the correct answer choice.

This explanation is still in progress. Please post any questions below!

[desmail]

Hi,

I'm having a little trouble with choices D and E. So if we negate choice E, it would weaken the argument because the stimulus says we need at LEAST ten parts water to 1 part fungicide. So for it to be more concentrated that means we would need less than ten parts water right? (more concentrated=less water needed)

I'm thinking D is wrong because the author already says that the fungicide has the capacity to eliminate the midlew completely (just because it has the capacity doesn't necessarily mean it will take it all off?)

Am I on the right track here? Any help would be appreciated!

Thanks,
Dana

[Jon Denning]

Hey desmail - thanks for the question, and I think you're more or less on the right track. This is a tricky one, where you need to recognize that the author's conclusion really depends on two keys ideas being simultaneously true: the fungicide needs to be able to kill the mildew completely, while at the same time being diluted enough so as not to harm the plants. The problem of course is that, while we know that both are possible individually, the author is having to assume that both can be true simultaneously. That's what E is saying: if you dilute it to the point it won't hurt the plant, it will still be effective enough to completely kill the mildew. Negating it would crush the argument, since its effectiveness would depend on it NOT being diluted enough to avoid hurting the plant.

D is wrong because it doesn't really relate to the argument. It doesn't matter how you define "effective" in general, since the author says this particular fungicide is "so effective that it has the capacity to eliminate".

I hope that helps!

[desmail]

Thanks for your reply! Ok I feel like I understand what youre saying, but lets just double check:

There seems to be a gap in the argument, we know that the dilution is safe for garden plants but we don't know the relationship between dilution and eliminating mildew and the author only addresses this relationship in the conclusion. So for the conclusion to be true, the author must assume that the amount of dilution will also be enough to be effective in eliminating the mildew.

This is where I get confused, when we negate E. If we negate E and say that its effectiveness depends on it being more concentrated, our conclusion only says that it has to be "sufficiently" diluted. The conclusion doesnt specify that it has to be exactly 10 parts to 1 part, it seems like the author is just saying that it must be around there by saying "at least." So if it is a little less or more concentrated I'm still having trouble seeing how that would affect anything.

Thanks for your help.

[Jon Denning]

Careful here. Don't get hung up on the 10:1 part. That's just the minimum amount we must water it down for it to be safe (so "sufficiently diluted" means at least that much; could be 20:1, etc). Less diluted than that--say 5:1--and we know it won't be completely harmless to the plants.

The potential problem is that for it to be safe it must be diluted at least that much, but once it's diluted by any amount we don't know if it will still be effective at killing all the mildew. We know it can potentially kill all the mildew, but if we dilute it (weaken it), which we MUST do for it to be safe for plants, then it's effectiveness can no longer be known. It might still work, but to conclude that it will the author has to assume it's still 100% effective even after being diluted to 10:1 or weaker. And that's what the correct answer says.

Make sense?

[desmail]

Got it! Thank you so much for your help!

[LSAT2018]

As a point of clarification, is answer choice E correct because it mentions that the fungicide causes no harm only if it is diluted AT LEAST to ten parts (premise) and AS LONG AS it is sufficiently diluted it is a means of eliminating mildew (conclusion)? In a sense, because the stimulus has discussed the minimum requirements, it is defending against the possibility that concentrations beyond the minimum determine the effectiveness of the fungicide?

Also, I was not able to eliminate answer choice B because I thought it defends against the possibility that the fungicide harms plants?

[James Finch]

Hi LSAT 2018,

The first premise in the stimulus lets us know that the fungicide does not harm plants when diluted 10:1 with water. Then next premise tells us how incredibly effective the fungicide is at eliminating powdery mildew from rose plants. But this second premise doesn't tell us whether this effectiveness varies depending on the dilution of the fungicide. This becomes an issue when the conclusion states that the fungicide will eliminate powdery mildew from rose plants without harming the plants, so long as it is diluted at least 10:1 with water.

We cannot draw the conclusion without knowing whether or not dilution affects the fungicide's effectiveness at eliminating powdery mildew. Answer choice (B) brings in information irrelevant to the argument, as the conclusion only addresses harm to plants, so this answer choice is out-of-scope. We can test this using the Assumption Negation technique:

No harm to people or animals Diluted 10:1, eliminates PM without risk to plants

Whereas answer choice (E), which addresses the missing link between dilution and effectives, would look like:

Effectiveness depends on being more than 10:1 water Diluted 10:1, eliminates PM without risk to plants

Here, (E) works because it tells us whether the fungicide is effective or not at the concentration safe for plants, making it the correct answer choice.

Hope this clears things up!