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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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Typically during thunderstorms most lightning strikes carry a negative electric charge; only a few carry a positive charge. Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires. The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

Type – weaken
Boil it down – Presence of positively charged smoke particles in storm causes extra positive strikes occur

(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.- irrelevant
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are. – the power of strikes is irrelevant
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is. – Irrelevant – likelihood of starting a forest fire is not a concern
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated. – Correct – Although the smoke particles have dissipated , the extra positive-charge strikes are still present
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire. – Irrelevant
Answer D
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
@Gmatninja, Experts,

Please Explain , Totally Stumped by this one
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
GMATNinja wrote:
Quote:
Typically during thunderstorms most lightning strikes carry a negative electric charge; only a few carry a positive charge. Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires. The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

Which of the following, if discovered to be true, most seriously undermines the hypothesis?

(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

kunal1608 wrote:
GMATNinja, Experts,

Please Explain , Totally Stumped by this one


So (D) is the best of the bunch.

I hope this helps!


Thankyou GMATNinja

Retrospectively, the only thing i think confused me is the reasoning given for the high occurrence of positive charge strikes. I got to thinking how can +ve attract +ve.

One more question, Do you recommend reading the question stem first for CR questions or do you think it hinders the ability to read/comprehend the details.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
GMATNinja wrote:
Quote:
Typically during thunderstorms most lightning strikes carry a negative electric charge; only a few carry a positive charge. Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires. The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

Which of the following, if discovered to be true, most seriously undermines the hypothesis?

(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

kunal1608 wrote:
GMATNinja, Experts,

Please Explain , Totally Stumped by this one

According to the author, smoky areas near forest fires probably have extra positive strikes because the smoke carries positively charged smoke particles into the air above a fire. So we need an answer choice that would undermine that hypothesis:

Quote:
(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.

We are trying to explain positive strikes, and we don't care about other kinds of rare lightning. Choice (A) does not impact the hypothesis, so it can be eliminated.

Quote:
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.

We are trying to explain why there are more positive strikes in smoky areas near forest fires. The hypothesis in question has nothing to do with how powerful the strikes are, so (B) can be eliminated.

Quote:
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.

Again, we are trying to explain WHY there are more positive strikes in smoky areas near forest fires. The likelihood of starting a forest fire has nothing to do with the hypothesis in question, so eliminate (C).

Quote:
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.

According to the hypothesis described by the author, smoky areas near forest fires probably have extra positive strikes because the smoke carries positively charged smoke particles into the air. In other words, the presence of extra positively charged particles (from the smoke) causes extra positive strikes. But choice (D) tells us that extra positive strikes still occur weeks after the charge of the smoke particles has dissipated. If the charge of the smoke particles has dissipated and we are still seeing extra positive strikes, then how can we blame the extra strikes on the smoke particles? Choice (D) undermines the hypothesis, so keep this one.

Quote:
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

This tells us that the TOTAL number of strikes is normal when there is a thunderstorm near a forest fire. However, this does not say anything about WHY there are more positive strikes near a forest fire. Choice (E) is not relevant to the hypothesis and can be eliminated.

So (D) is the best of the bunch.

I hope this helps!


Hi GMATNinja

Statement given in the stimulus - "Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires."

My inference - High proportions of positive-charge strikes are more powerful than otherwise positive charge strikes.

Based on this inference, I chose answer B.

Is my inference absolutely wrong? Shouldn't extra positive charge strike be more powerful than normal positive strike?

Please resolve. Thanks in advance.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
2
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This is a Cause and Effect type question.

Conclusion------- Smoke particles cause +ve charge strikes

Possible weakeners ----
1. Something else does this
2.Could be the reverse case (though not logical for this question)
3. +ve charged strike happens first, then smoke
4. No smoke particles but still +ve charged strike.

D ---- says the number 4 option from above.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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Official Answer:-

Argument Evaluation

Situation Thunderstorms with unusually high proportions of positive-charge lightning strikes tend to occur in smoky areas near forest fires. Smoke carries positively charged particles into the air above fires, suggesting that smoke particles in storm clouds are responsible for the higher proportion of positive strikes.

Reasoning What would cast doubt on the hypothesis that the extra positive-charge lightning strikes in thunderstorms near forest fires result from positively charged smoke particles carried into the storm clouds? The hypothesis would be weakened by evidence that the positively charged smoke particles do not enter the storm clouds in the first place, or that they do not retain their charge in the clouds long enough to produce an effect, or that their positive charge cannot affect the charges of the storm’s lightning strikes in any case, or that some other factor tends to make the lightning strikes above these storms positively charged.

Quote:
(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.

A It could be that positively charged smoke particles cause these other kinds of rare lightning, too, so this does not seriously undermine the hypothesis.

Quote:
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.

B The hypothesis is not about the power of the positive-charge lightning strikes, only about why a high proportion of them occur in thunderstorms near forest fires.

Quote:
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.

C The hypothesis is about why positive-charge strikes tend to occur in smoky areas near forest fires that have already started before the strikes occur. Furthermore, an equal likelihood of positive-charge and negative-charge strikes starting fires cannot explain a correlation between fi res and positive-charge strikes specifically.

Quote:
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.

D Correct. This means that even when drifting clouds of smoke persist for weeks after a fire, when the charge of their particles has already dissipated, the smoke somehow still makes the strikes positively charged in any thunderstorms arising within it. If so, some factor other than positively charged smoke particles must affect the strikes’ charge.

Quote:
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

E This information does not undermine the hypothesis. The hypothesis does not concern the possibility that there might be more lightning strikes in the vicinity of forest fires; rather it concerns the proportion of all such lightning strikes that are positively charged.

The correct answer is D.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
GMATNinja wrote:
Quote:
Typically during thunderstorms most lightning strikes carry a negative electric charge; only a few carry a positive charge. Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires. The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

Which of the following, if discovered to be true, most seriously undermines the hypothesis?

(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

kunal1608 wrote:
GMATNinja, Experts,

Please Explain , Totally Stumped by this one

According to the author, smoky areas near forest fires probably have extra positive strikes because the smoke carries positively charged smoke particles into the air above a fire. So we need an answer choice that would undermine that hypothesis:

Quote:
(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.

We are trying to explain positive strikes, and we don't care about other kinds of rare lightning. Choice (A) does not impact the hypothesis, so it can be eliminated.

Quote:
(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.

We are trying to explain why there are more positive strikes in smoky areas near forest fires. The hypothesis in question has nothing to do with how powerful the strikes are, so (B) can be eliminated.

Quote:
(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.

Again, we are trying to explain WHY there are more positive strikes in smoky areas near forest fires. The likelihood of starting a forest fire has nothing to do with the hypothesis in question, so eliminate (C).

Quote:
(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.

According to the hypothesis described by the author, smoky areas near forest fires probably have extra positive strikes because the smoke carries positively charged smoke particles into the air. In other words, the presence of extra positively charged particles (from the smoke) causes extra positive strikes. But choice (D) tells us that extra positive strikes still occur weeks after the charge of the smoke particles has dissipated. If the charge of the smoke particles has dissipated and we are still seeing extra positive strikes, then how can we blame the extra strikes on the smoke particles? Choice (D) undermines the hypothesis, so keep this one.

Quote:
(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

This tells us that the TOTAL number of strikes is normal when there is a thunderstorm near a forest fire. However, this does not say anything about WHY there are more positive strikes near a forest fire. Choice (E) is not relevant to the hypothesis and can be eliminated.

So (D) is the best of the bunch.

I hope this helps!


GMATNinja




Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated. << "weeks after the charge of the smoke particles has dissipated". However, the cloud of smoke have extra positive-charge following the forest fire or event that released smoke particles.

In choice (D), is it possible to interpret that cloud may keep/contain tons of positive-charge or time is required to form amount of positive-charge?
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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Tanchat wrote:

GMATNinja


Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated. << "weeks after the charge of the smoke particles has dissipated". However, the cloud of smoke have extra positive-charge following the forest fire or event that released smoke particles.

In choice (D), is it possible to interpret that cloud may keep/contain tons of positive-charge or time is required to form amount of positive-charge?

We know from the passage that "smoke carries positively charged smoke particles into the air above a fire."

In other words, at some point while a fire is in progress, there are positively charged smoke particles above that fire. The author argues that these particles cause extra positive lightning strikes.

Then (D) comes along and tells us that clouds of smoke from fires drift around for weeks, and that the positively-charged particles dissipate within that time.

So, it's not that clouds keep a positive charge or gain a positive charge -- as time goes on, the clouds actually lose their positive charge.

Even after these particles lose their charge, there are still extra positively-charged strikes. This hurts the link that the author draws between the positively-charged particles and the positively-charged lightning strikes. There must be some other explanation for the strange lightning.

I hope that helps!
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
Hi avigutman - i have a fundamental question here. The hypothesis made in the argument is based on correlation / causation

Per my understanding of the theory

Quote:

Argument : X and Y are seen together
Hypothesis : X is causing Y

Weakeners
(weakener 1) Y causes X
(weakener 2) Z causes X and Y

The following are NOT CONSIDERED WEAKENERS
(weakener 3) X is seen and Y does not follow
(weakener 4) Y happens without X

(weakener 3) and (weakener 4) are NOT weakeners because (3) and (4) go against the premise -- (weakener 3) and (weakener 4) weaken the premise THAT X and Y are seen together

So (Weakener 3) and (weakener 4) are not true weakeners of the argument

That is my understanding of the theory at-least


Originally posted by jabhatta2 on 16 Jun 2022, 08:23.
Last edited by jabhatta2 on 16 Jun 2022, 08:36, edited 8 times in total.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
^^^ I thought option (D) did was weakener type 4 above

All option (D) does is weaken the premise that X and Y are seen together

Is my understanding of the theory wrong perhaps ? Perhaps (3) and (4) are weakeners, i am not sure. Other possibility is perhaps, this is NOT a correlation/causation problem to begin with - i am not sure..

In the context of the problem

Quote:
X = positively charged smoke particles
Y = positive-charge strikes

X and Y are seen together
hence, hypothesis is : X causes Y
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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jabhatta2 wrote:
I thought option (D) did was weakener type 4 above
All option (D) does is weaken the premise that X and Y are seen together

Forcing memorized templates onto new arguments will cap your potential, jabhatta2, because every argument has unique characteristics.
Let's look at the premise and at answer choice (D) and see what we think.
Premise:
Quote:
Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires.

Answer choice (D):
Quote:
Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.

What do you think?

More generally:
jabhatta2 wrote:
Argument : X and Y are seen together
Hypothesis : X is causing Y

Weakeners
(weakener 1) Y causes X
(weakener 2) Z causes X and Y

The following are NOT CONSIDERED WEAKENERS
(weakener 3) X is seen and Y does not follow
(weakener 4) Y happens without X

(weakener 3) and (weakener 4) are NOT weakeners because (3) and (4) go against the premise -- (weakener 3) and (weakener 4) weaken the premise THAT X and Y are seen together

Weakeners 3 and 4 only go against the premise if the premise is phrased thusly:
X and Y are only ever seen together; X is never observed in the absence of Y, and Y is never observed in the absence of X.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
avigutman why not C?If C is true then positive strike will cause fire how can we conclude relation b/w postively charged particles in storm clouds and the strike since we know that smoke only goes above the fire and since fire will not be there already we cannot ay postively charged particles are already present and hence cant present a relation
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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Elite097 wrote:
avigutman why not C?If C is true then positive strike will cause fire how can we conclude relation b/w postively charged particles in storm clouds and the strike since we know that smoke only goes above the fire and since fire will not be there already we cannot ay postively charged particles are already present and hence cant present a relation

Yes, Elite097, (C) tells us that positive strikes can cause fires too. You used the word “relation” a couple of times in your post. Not sure what you mean. If you want to get a response, please try to lay out your argument in a more readable way, and check for typos and punctuation before you post.

Posted from my mobile device
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
GMATNinja KarishmaB @Experts.

The hypothesis is that - Extra positive strikes occur because of the presence of such (Smoke particles) particles in the storm clouds.

D) says - thunderstorms that occur in drifting clouds of smoke have extra +ve charge strikes weeks after the CHARGE of the smoke particles has dissipated. (not the smoke particles themselves, they could still be there, and infact presumably are still there as mentioned in the OG explanation that ("this means that even when drifting clouds of smoke persist....").

Nowhere does the hypothesis claim that these smoke particles HAVE to be +vely charged to cause the +ve strikes. All it says is that the smoke particles cause the strikes, which they could still be doing even when their positive charge has dissipated. (Presumably by giving their +ve charge to other elements which are causing the strikes in which case they are still the cause albeit an indirect cause.

Would appreciate thoughts from Experts, GMATNinja, KarishmaB etc.

Thanks!
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
PReciSioN wrote:
GMATNinja KarishmaB @Experts.

The hypothesis is that - Extra positive strikes occur because of the presence of such (Smoke particles) particles in the storm clouds.

D) says - thunderstorms that occur in drifting clouds of smoke have extra +ve charge strikes weeks after the CHARGE of the smoke particles has dissipated. (not the smoke particles themselves, they could still be there, and infact presumably are still there as mentioned in the OG explanation that ("this means that even when drifting clouds of smoke persist....").

Nowhere does the hypothesis claim that these smoke particles HAVE to be +vely charged to cause the +ve strikes. All it says is that the smoke particles cause the strikes, which they could still be doing even when their positive charge has dissipated. (Presumably by giving their +ve charge to other elements which are causing the strikes in which case they are still the cause albeit an indirect cause.

Would appreciate thoughts from Experts, GMATNinja, KarishmaB etc.

Thanks!


ChiranjeevSingh GMATGuruNY MartyMurray AjiteshArun Sajjad1994 Bunuel would appreciate your inputs please!
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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PReciSioN wrote:
The hypothesis is that - Extra positive strikes occur because of the presence of such (Smoke particles) particles in the storm clouds.

Let's go back and see what the passage says.

The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

"Such" before "particles" toward the end of the sentence is a look above marker. So, to correctly understand the meaning of the sentence, we must correctly identify what "such particles" refers to.

Looking back, we see that such particles refers to "positively charged smoke particles." So, the sentence communicates that the hypothesis is that the extra positive strikes occur because of the presence of "POSITIVELY CHARGED smoke particles" in the smoke clouds.

So, what the passage indicates and what you indicated are a little different. Whereas you indicated that "such particles" means "such (Smoke particles), the passage indicates that "such particles" refers to "positively charged smoke particles."

Quote:
Nowhere does the hypothesis claim that these smoke particles HAVE to be +vely charged to cause the +ve strikes.

We see that, actually, the hypothesis does involve "positively charged" smoke particles.

Thus, the correct answer weakens the case for the hypothesis by showing that the effect, "extra positive-charge strikes," still occurs when the hypothesized cause, "positively charged smoke particles," is no longer present.
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Re: Typically during thunderstorms most lightning strikes carry a negative [#permalink]
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MartyMurray wrote:
PReciSioN wrote:
The hypothesis is that - Extra positive strikes occur because of the presence of such (Smoke particles) particles in the storm clouds.

Let's go back and see what the passage says.

The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

"Such" before "particles" toward the end of the sentence is a look above marker. So, to correctly understand the meaning of the sentence, we must correctly identify what "such particles" refers to.

Looking back, we see that such particles refers to "positively charged smoke particles." So, the sentence communicates that the hypothesis is that the extra positive strikes occur because of the presence of "POSITIVELY CHARGED smoke particles" in the smoke clouds.

So, what the passage indicates and what you indicated are a little different. Whereas you indicated that "such particles" means "such (Smoke particles), the passage indicates that "such particles" refers to "positively charged smoke particles."

Quote:
Nowhere does the hypothesis claim that these smoke particles HAVE to be +vely charged to cause the +ve strikes.

We see that, actually, the hypothesis does involve "positively charged" smoke particles.

Thus, the correct answer weakens the case for the hypothesis by showing that the effect, "extra positive-charge strikes," still occurs when the hypothesized cause, "positively charged smoke particles," is no longer present.


Thanks Marty! :) That makes sense. I agree with your explanation.
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