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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]

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02 Apr 2008, 17:50
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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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an 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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02 Apr 2008, 18:36
A - thats what directly attacks the assumption that we can figure out the earths age by taking last 100 years data.

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02 Apr 2008, 19:23
notahug 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an 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 got E, and hello bsd.
The conclusion of this passage is that "you can determine the age of the ocean by measuring increase in ocean's salt level and river salt deposit"
My assumption: River is the only source of salt deposit

B is just irrelevant. The stems did not mention anything about river's salt level.
C is also irrelevant. No mention of Ocean's floor salt.
D is also irrelevant. There maybe a superior method, but not mention here. The stems only say an "accurate method", not the best method.

Comes down to A and E for me. I eliminated A because it is weak. If there has been a few unusually high salt deposits, we can still relatively measure the age of the ocean accurately. For E, if salt is used up by biological activity, there is no way to measure the ocean's age accurately.

E for me.

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03 Apr 2008, 00:05
bkk145 wrote:
notahug 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an 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 got E, and hello bsd.
The conclusion of this passage is that "you can determine the age of the ocean by measuring increase in ocean's salt level and river salt deposit"
My assumption: River is the only source of salt deposit

B is just irrelevant. The stems did not mention anything about river's salt level.
C is also irrelevant. No mention of Ocean's floor salt.
D is also irrelevant. There maybe a superior method, but not mention here. The stems only say an "accurate method", not the best method.

Comes down to A and E for me. I eliminated A because it is weak. If there has been a few unusually high salt deposits, we can still relatively measure the age of the ocean accurately. For E, if salt is used up by biological activity, there is no way to measure the ocean's age accurately.

E for me.

KONG!
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03 Apr 2008, 02:10
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notahug 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an 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.

It's between A and E. In an exam I would have gone for A. My reasoning is as follows;

conclusion states that: 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Inorder for this to be possible the author must assume that the the salt dissolved in the earth's oceans not been unusually large. if they have been then it will be difficult to accurately estimate the maximum age of the earth's oceans.

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years. (Hold it, If the quantities have been large it will be difficult to accurately determine the age of the earth's oceans)
B. At any given time, all the Earth’s rivers have about the same salt levels (This could be possible but it does not directly affect the argument).
C. There are salts that leach into the Earth’s oceans directly from the ocean floor. (Unecessary and out of scope. Remember we are concerned with salt from rivers)
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans. (Even if there is the argument is not saying that this is the best method. So is therefore unecessary)
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. (This is a tricky one, I guess this can be assumed to because if they were then it our estimates will be flawed. However, A seems more precise it refers to salt from rivers which the argument is based on. E just seems to general whilst A is more precise and in line with the argument)

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03 Apr 2008, 03:01
Haha couldn't have put it better myself. Kudos vivali.

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03 Apr 2008, 03:02
Vavali wrote:
notahug 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an 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.

It's between A and E. In an exam I would have gone for A. My reasoning is as follows;

conclusion states that: 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Inorder for this to be possible the author must assume that the the salt dissolved in the earth's oceans not been unusually large. if they have been then it will be difficult to accurately estimate the maximum age of the earth's oceans.

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years. (Hold it, If the quantities have been large it will be difficult to accurately determine the age of the earth's oceans)
B. At any given time, all the Earth’s rivers have about the same salt levels (This could be possible but it does not directly affect the argument).
C. There are salts that leach into the Earth’s oceans directly from the ocean floor. (Unecessary and out of scope. Remember we are concerned with salt from rivers)
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans. (Even if there is the argument is not saying that this is the best method. So is therefore unecessary)
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. (This is a tricky one, I guess this can be assumed to because if they were then it our estimates will be flawed. However, A seems more precise it refers to salt from rivers which the argument is based on. E just seems to general whilst A is more precise and in line with the argument)

On Second thought's I go for E. A even though it may be necessary, the assumption (necessary for the argument to hold) is not as vital as in 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 have been used up by biological activity then we will not be able to derive an accurate estimate of the ocean's age.

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03 Apr 2008, 03:04
I take that kudos back

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03 Apr 2008, 04:03
bsd_lover wrote:
I take that kudos back

Sorry Bbsd_lover I didn't mean to sell you out there.

It's just the Einstein in me deciding it's E!

Can we have the OA please?

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03 Apr 2008, 05:49
i will go with A here.
My Explanation.

A says that the amount of salt deposited is not unsually high.
it this is not the assumption and if the Amount of salt is unusally high in the past few years, then it doesnt make calculation simple.
if over the years the % increase in salt is 10%, i.e now 110.. once 100, then doing a back ward calculation we can calculate the age.
this would hold good only if the salt deposition is uniform throughout.

I reject E because, it talks about something that has been happening over the complete period of time.
So, it doesnt have any implact on the discussion on the salt deposition.

Anyways, whats the OA ?

regards,
Kiran

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03 Apr 2008, 06:09
OA is A. But I still do not agree, E for me, although I read all of you guys reasoning.

Simply thinking, what happen if E is wrong? Nothing can be caculated
What happen if A is wrong? We still caculate the age of Earth

Anyone can explain further? How can you come up with A? Could you bold the key words that make you think A ?
Is that "hundred year" so important in this passage? Someone said that it is the KEY

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03 Apr 2008, 06:23
B

I guessed that it is easy one and B is obvious but I'm really surprised when have read the thread.
I will post my reasons a bit later.
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03 Apr 2008, 06:42
Neochronic wrote:
i will go with A here.
I reject E because, it talks about something that has been happening over the complete period of time.
So, it doesnt have any implact on the discussion on the salt deposition.

Anyways, whats the OA ?

regards,
Kiran

Like this reasoning! That really makes sence. Now I understand why the OA is A.
The "past hundred years" is really important Key. It is the REPRESENTATIVE for the scientists to caculate the Earth's age. If it is unusually high than hundred and thousand years prior to it, then it can not a representative!

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03 Apr 2008, 06:48
walker I am with you, it has to be B. A can't be the OA. We are talking about the life of the ocean, 100 years is such a small subset. B is saying the same thing at A, but also broadcasting that across the life of the ocean.

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03 Apr 2008, 06:52
ok ok on second thought it doesnt have to be B, it has to be A.

We are talking about dissolved salts, not salts that is stated in B

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03 Apr 2008, 07:24
really tough .... "unusual" is not clear for me.....

BTW I found a few threads with OA=A and a few ones with OA=E .....
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03 Apr 2008, 07:32
walker wrote:
:? really tough .... "unusual" is not clear for me.....

BTW I found a few threads with OA=A and a few ones with OA=E .....

Well, so.. pls post their reasonings for both OAs.

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03 Apr 2008, 07:51
notahug wrote:
Well, so.. pls post their reasonings for both OAs.

I guess E is wrong.

E. None of the salts carried into the Earth's oceans by rivers are used up by biological activity in the oceans.

to make E a good assumption we have to add following:
1. the salts is used by biological activity in the oceans and is not returned to the oceans.
2. biological activity varied during centuries.
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03 Apr 2008, 14:13
Ok here's my detailed reasoning. Its not that I didn't see E or didn't understand what it says. I looked at both and I just smelled a GMAT trap by looking at E. It just didn't seem directly relevant to the main argument which was : "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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated."

If we look at A : "The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years." we can see a direct relation to the assumption. In the GMAT - the more direct relation to the main argument always wins. Even though E looks VERY seductive. Again, we can argue for days about what is more correct - but the important thing is what the GMAT will deem correct.

What was the source of this question ?

ps. Even Einstein sold me out, only one person agreed with me - thanks kkkkkiran

notahug 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 oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an 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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03 Apr 2008, 19:32
notahug wrote:
Neochronic wrote:
i will go with A here.
I reject E because, it talks about something that has been happening over the complete period of time.
So, it doesnt have any implact on the discussion on the salt deposition.

Anyways, whats the OA ?

regards,
Kiran

Like this reasoning! That really makes sence. Now I understand why the OA is A.
The "past hundred years" is really important Key. It is the REPRESENTATIVE for the scientists to caculate the Earth's age. If it is unusually high than hundred and thousand years prior to it, then it can not a representative!

Flaw of the this argument is that the conclusion is based solely on a belief that "the history of the salt carried by the river will be repeated every year, so over past hundreds of years". Nothing change with the repetition will be assumption here and therefore helps to confirmed that the age can be accurately estimated.

E win!
A. No matter how large or not large the quantities of salt is adready the fact

E.
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# The Earth s rivers constantly carry dissolved salts into its

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