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Typically during thunderstorms most lightning strikes carry a negative

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Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 30 May 2017, 21:34
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The Official Guide for GMAT Verbal Review 2018

Practice Question
Question No.: CR 179
Page:

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.

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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 05 Nov 2017, 22:25
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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.

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!
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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 31 May 2017, 01:24
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]

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New post 31 May 2017, 01:59
D. When smoke particles dissipates then there are thunderstorms with extra positive charge.

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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 04 Sep 2017, 03:02
Thank you so much for your useful explanation.
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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 26 Oct 2017, 11:18
@Gmatninja, Experts,

Please Explain , Totally Stumped by this one
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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 26 Oct 2017, 11:20
hazelnut wrote:
The Official Guide for GMAT Verbal Review 2018

Practice Question
Question No.: CR 179
Page:

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.


I chose A as it suggests that there is some alternate cause for the lightning near the fires
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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 10 Nov 2017, 02:58
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]

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New post 19 May 2018, 07:46
Here I was confused with Cause - effect in conclusion pls correct me if I am wrong.

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.


Cause-+ve particles in clouds(presence of such particles in the storm clouds)
Effect-extra +ve particles in smoke( the extra positive strikes occur)
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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 22 Jul 2018, 09:49
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]

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New post 17 Aug 2018, 07:00
I'm seeing confusion over the phrases "positive charge" and "positive particles" in this argument. The key to clearing up this confusion is to recognize that this argument basically has nothing to do with positives or negatives.

The author argues that 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 positively charged particles (from the smoke) causes extra positive strikes.

Let me put this another way: The author argues that smoky areas near forest fires probably have extra goldfish strikes because the smoke carries groovy smoke particles into the air. In other words, the presence of groovy particles (from the smoke) causes extra goldfish strikes.

I've just substituted complete nonsense into the argument, but the logic is exactly the same: more of a certain kind of particle leads to more of a certain kind of strike. In this case, they happen to be called "positively charged" particles and "positive" strikes. But the argument essentially says that if you add more of X, then you get more of Y.

KGump wrote:
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

We don't care about how the actual science of electricity works, and GMAT questions will NEVER test you on your science knowledge. In this case, you only care about undermining the hypothesis that "the extra positive strikes occur because of the presence of such particles in the storm clouds."

KGump wrote:
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.

I don't feel strongly about this, one way or another. Historically, large test-prep companies have often made a big deal out of this ("read the question first, it's magical!!!"), and I think that's misguided -- if reading the question first helps, it won't help much, and it can't do anything for you on RC, since you can't even see all of the questions.

Personally, I don't read the question first, because I'll ultimately need to have a flawless understanding of both the structure of the passage and the author's language choices. When you read the question first, there's some risk that you'll be so hyped up about looking for something specific (an assumption or a way to strengthen something, or whatever) that you won't read with as much precision as you would otherwise. I don't think that the risk is huge, though. So do whatever works best for you, as long as you're breaking down the structure of the argument with precision.

XYZABCABC wrote:
HiGMATNinja
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.

Remember to stay focused on the exact question we have been asked.

This question asks us to undermine the hypothesis. The hypothesis is that "positively charged smoke particles in an area lead to extra positive lightning strikes in that area." This hypothesis has nothing to do with how powerful a positive lightning strike is. It has to do with how many positive lightning strikes there are.

To clarify the language: if I say that cities have an unusually high proportion of car accidents in August, I don't mean that the car accidents are especially severe in August. I'm just saying that there's a greater number of car accidents in August.

I hope this helps!
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Re: Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 15 Sep 2018, 09:44
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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New post 08 Oct 2018, 22:51
(A) Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.
point of concern is fire vs positive charged thunders. hence gimmick: relevant but out of scope

(B) The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.
strength f the strike is not a concern. gimmick: relevant but out of scope

(C) A positive-charge strike is as likely to start a forest fire as a negative charge strike is.
this is reversing the causal relationship but it also saying about negative charge strike. hence its not a concrete
reversal.

(D) Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.
relevant since no positive charged smoke is present but positive charge thunder is striking. hence eliminating the causal
relationship.

(E) The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.
might be a relevant point but its way too overboard. it is not addressing the concern. its vague not so clear enough.
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Typically during thunderstorms most lightning strikes carry a negative  [#permalink]

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New post 26 Oct 2018, 02:16
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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