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The Earth's rivers constantly carry dissolved salts into its

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The Earth's rivers constantly carry dissolved salts into its [#permalink] New post 06 Jan 2008, 16:04
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The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
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Re: CR- Assumption [#permalink] New post 06 Jan 2008, 16:35
I think the assumption is that the increase in salt level is constant throughout time. So, I think A is the answer. If the increase in level over the last 100 years in unusually high, then that invalidates the method.
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Re: CR- Assumption [#permalink] New post 06 Jan 2008, 17:15
msday86 wrote:
I think the assumption is that the increase in salt level is constant throughout time. So, I think A is the answer. If the increase in level over the last 100 years in unusually high, then that invalidates the method.


I agree with you that A is right. However, what do you think about E?
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Re: CR- Assumption [#permalink] New post 06 Jan 2008, 18:02
Expert's post
ttram wrote:
msday86 wrote:
I think the assumption is that the increase in salt level is constant throughout time. So, I think A is the answer. If the increase in level over the last 100 years in unusually high, then that invalidates the method.


I agree with you that A is right. However, what do you think about E?


After re-reading choice E several times (which I may not have done on the real GMAT), it seems to be irrelevant.
The argument says to take the difference between salt levels today and 100 years ago and then divide the total salt level by the difference. Choice E says that there may be some biological activities using up the salts, which is fine since these biological activities have been active longer than 100 years, so they are a constant. Every 100 years these biological activities consumed the same amount of salt. Surprisingly, choice E can be ruled out mathematically.
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Re: CR- Assumption [#permalink] New post 06 Jan 2008, 18:16
bb wrote:
ttram wrote:
msday86 wrote:
I think the assumption is that the increase in salt level is constant throughout time. So, I think A is the answer. If the increase in level over the last 100 years in unusually high, then that invalidates the method.


I agree with you that A is right. However, what do you think about E?


After re-reading choice E several times (which I may not have done on the real GMAT), it seems to be irrelevant.
The argument says to take the difference between salt levels today and 100 years ago and then divide the total salt level by the difference. Choice E says that there may be some biological activities using up the salts, which is fine since these biological activities have been active longer than 100 years, so they are a constant. Every 100 years these biological activities consumed the same amount of salt. Surprisingly, choice E can be ruled out mathematically.


Thanks. Now, I got it :-D .
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Re: CR- Assumption [#permalink] New post 06 Jan 2008, 19:05
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


I think E is right.

Evidence states that "The Earth's rivers constantly carry dissolved salts into its oceans."
Therefore, A is the paraphasing of the evidence. (Not the assumption of the author)

The author's assumption is "There has been [no reduction] in salt level in the oceans"
E is paraphasing this assumption.
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Re: CR- Assumption [#permalink] New post 06 Jan 2008, 20:45
alnasl wrote:
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


I think E is right.

Evidence states that "The Earth's rivers constantly carry dissolved salts into its oceans."
Therefore, A is the paraphasing of the evidence. (Not the assumption of the author)

The author's assumption is "There has been [no reduction] in salt level in the oceans"
E is paraphasing this assumption.


I think D it is

The argument focuses on the resulting increase in salt levels[/b], [b]not the salt itself. So E is out

if there is any other way to estimate accurately the maximum age of the ocean, the argument will be fallen.

D defends the argument by saying that taking the resuling increase in salt levels and ...is only method to accurately estimate the maximum age of the ocean.
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Re: CR- Assumption [#permalink] New post 07 Jan 2008, 03:23
E it is...
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Re: CR- Assumption [#permalink] New post 07 Jan 2008, 08:09
I go with D also.

Choice E mentions rivers, which is beyond the scope; moreover rivers have no salt, so again is beyond the scope.

The argument assumes that there is no other method to check the lifespan of the earth but my measuring it's salt levels. Choice D is the closest.

What is the OA?
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Re: CR- Assumption [#permalink] New post 08 Jan 2008, 03:52
I will go with E
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Re: CR- Assumption [#permalink] New post 08 Jan 2008, 14:08
I think B is the right answer.

The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.[/quote]
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Re: CR- Assumption [#permalink] New post 09 Jan 2008, 11:33
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


We can eliminate B, C and D after reading.
The argument is talking about: We can guess the maximum Earth's age when we calculate dissolved salts from rivers to oceans with the premise is at the first time, the salt level of oceans is zero.

B: Irrelevant because we do not discuss about salt level in rivers. It does not lead us to the conclusion.
C: Irrelevant, too.
D: Although it seems to be a right answer because it talks about a method. However, it is too general, and not assume anything.
E: The first time, I think E is the best answer. However, it is a mistake. First, it is too specific. If none of the salts were used by biological activity, so, how about other activities? (such as physical activity, chemical activity...)? Second, it does not lead us to a conclusion. We cannot conclude that the method is accurate because of the premise E.
A: It supports the premise:
Premise:
- At the first time, the salt level of oceans is zero.
- We calculate the salt level of oceans in the past hundred years, and we can know the Earth's age.
- In a process, the quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
- Thus, we can convince that the result is believable.

I hope that you guys can accept my explanation.
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Re: CR- Assumption [#permalink] New post 10 Jan 2008, 10:34
Sounds good to me. I vote for E.

I voted for B initially because I mistakenly thought "At any given time, all the Earth’s rivers have about the same salt levels." was "At any given time, all the Earth's oceans have about the same salt levels." :(

What is the right answer?

ttram wrote:
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


We can eliminate B, C and D after reading.
The argument is talking about: We can guess the maximum Earth's age when we calculate dissolved salts from rivers to oceans with the premise is at the first time, the salt level of oceans is zero.

B: Irrelevant because we do not discuss about salt level in rivers. It does not lead us to the conclusion.
C: Irrelevant, too.
D: Although it seems to be a right answer because it talks about a method. However, it is too general, and not assume anything.
E: The first time, I think E is the best answer. However, it is a mistake. First, it is too specific. If none of the salts were used by biological activity, so, how about other activities? (such as physical activity, chemical activity...)? Second, it does not lead us to a conclusion. We cannot conclude that the method is accurate because of the premise E.
A: It supports the premise:
Premise:
- At the first time, the salt level of oceans is zero.
- We calculate the salt level of oceans in the past hundred years, and we can know the Earth's age.
- In a process, the quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
- Thus, we can convince that the result is believable.

I hope that you guys can accept my explanation.
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Re: CR- Assumption [#permalink] New post 10 Jan 2008, 11:39
I will go with E here.
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Re: CR- Assumption [#permalink] New post 10 Jan 2008, 12:20
I am confused between B and E. If i have to choose i will go with E
whts the QA?
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Re: CR- Assumption [#permalink] New post 10 Jan 2008, 12:39
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


Well argument assuming that all the salts come from rivers otherswise we will not be able to use the method defined in the argument.
Try negating E and see if the result statements weaken the argument if it does we have our answer.

Opposite of E:
Some of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.

argument does not stand and Opposite of E actually weakens the argument.
E.
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Re: CR- Assumption [#permalink] New post 13 Jan 2008, 09:44
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.

dude, whats the OA here?
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Re: CR- Assumption [#permalink] New post 13 Jan 2008, 09:48
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


If the salts were partly used up by biological activity, then the level would be affected and the result would be inaccurate. E is the best choice
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Re: CR- Assumption [#permalink] New post 13 Jan 2008, 15:35
marcodonzelli wrote:
ttram wrote:
The Earth's rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.

Which of the following is the assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


If the salts were partly used up by biological activity, then the level would be affected and the result would be inaccurate. E is the best choice


The OA is A
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Re: CR- Assumption [#permalink] New post 13 Jan 2008, 16:48
Argument does not depend on what is discussed in E as 'biological activity' has no relevance. Clearly A is our answer.
Re: CR- Assumption   [#permalink] 13 Jan 2008, 16:48
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