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

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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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06 Jan 2017, 20:01
alpha_plus_gamma wrote:
priyankur_saha@ml.com wrote:
IMO E.
* The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
Deposit could be large but that never hampers the result

If the quantities of dissolved salts deposited by rivers in the Earth’s oceans have been unusually large during the past hundred years , it will surely affect the result.

Consider the salts deposited in the past century is X.

The current salt level is say 5X

so as per the result ocean's age is 5 centuries.

But if X is unusually large and the deposited salt level of previous centuries were say only X/4 per century then the result will have a blunder!

Lets see in E :

by your same anology .
Current salt level = 500 billion tons ;
estimated age = 500 million years .

but 200 billion tons are used by organisms by now.
Actual age = 700 million years . but estimated is just 500 milllion years .

IMO A and E . but am still confused in my opinion both A and E are right assumptions .
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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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14 Feb 2017, 13:50
Tough question! Clearly the answer is either A or E. When I get stuck like this I look for clues within the argument wording. The argument mentions "increases & decreases" which deal with numbers. Answer A contains "quantities" which is also a word associated with numbers. Therefore, I was confident in selecting "A".
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The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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15 Feb 2017, 10:16
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.

Note:Assumption question askes to find the link that connects the premise to the conclusion and the choice that explains the transition from the premise to the conclusion in the best and accurate way is the answer.

Choice A if the quantities of the dissoved salts be different over the past hundred years then the argument method to find the age of the earth would not be valid.since the data would be inconsistent. So this is the best choice for an assumption question.
Choice B The difference in the level of dissoved salt in different rivers is not the point of disccusion and also the difference can be determined and then the calculations can be done.
Choice C the choice is out of scope as this will not support the plan.
Choice D the superiority of the method is not under scrutininy but the feasibility is. so out of scope.
Choice E the salt used for the biological activities still remain in the ocean so does not impact the result.
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The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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14 May 2017, 07:40
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.

GMATNinja & GMATNinjaTwo (A), (B) and (E) are pretty close to each other. How to eliminate the incorrect answer choices?
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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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14 May 2017, 12:53
hits wrote:
Only B & E makes sense

B : only if the salt content carried by the river is constant, will the calculation of salt content in the ocean be possible.

E : this seems to more directly implied than the previous one.

Hence I would go with E

Whats the OA??

The OA is A, here you need to use the negation technique. to find the assumption.
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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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20 May 2017, 18:26
hazelnut 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.

GMATNinja & GMATNinjaTwo (A), (B) and (E) are pretty close to each other. How to eliminate the incorrect answer choices?

As for choice (B), we don't care about the relative salt levels in the individual rivers, only about the cumulative amount of salt carried into the oceans. It doesn't matter if some rivers carry more salt than others.

As for choice (E), "taking the resulting increase in salt levels in the oceans over the past hundred years" will tell us how much the salt levels increased DESPITE loss of salt due to biological activity (or any other factor that would reduce salt levels in the ocean). If the impact of these factors is small, these factors will not significantly affect the calculations. In other words, it is okay if A SMALL AMOUNT of salt is used up by biological activity in the oceans.

This thread contains several other posts explaining (B) and (E), so please review these before posting additional questions.
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The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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02 Jun 2017, 01:29
Assume we know in hundred years salt level increases by 10 units and 1 unit is used by biological activity. So effectively salt level increases by 9 units every hundred years. So if we know increase in the salt level in the past hundred years ,we can find out how long it took to reach the current level from salt free level even if some salt is used by biological activity. The biological activity would have been there all along. E need not be assumed
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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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17 Jun 2017, 14:23
I haven't considered about the time frame somehow.
I did not notice "hundred years"
and did not even think about the biological activity is sth. constant during the whole time span.
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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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08 Nov 2017, 09:55
a little input from my perspective to help anyone who made the same mistake as I did. i picked E for this answer and I now know why E is wrong.

My reason for picking E was
if we negate A, yes the large amount of salt will effect the result, making it inaccurate, but the method itself is still sound, we can still determine the age by measuring the salt level, it's just not as accurate.
When i negate E, i made the mistake by deleting none, i assumed the result was Salt carried into ocean are used up by biological activities. So if the salt are used up, we would have 0 salt content in the ocean, thus the method would fail. So I picked E.

but after reading the previous comments on this thread, i noticed you are suppose to change None to Some when you apply negation. If I did that, then the meaning changed to some of the salt is used up by biological activities. That activity could be constant so it is irrelevant to the conclusion.

Hope this helps.
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Re: The Earth's rivers constantly carry dissolved salts into its oceans. [#permalink]

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08 Nov 2017, 11:47
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.

At first i answered wrongly. but after reading explanation, I can understand that A is the assumption.

Premises : Ocean's salt concentration is increasing constantly as river flows into it.
Conclusion : By using this, we can calculate the age of the oceans. how ? just using a formula. First we calculate how much salt concentration is increased for past 100 year, then currently how much salt concentration ocean has. If we divide both, we can find the age of the ocean.

Assumption : Calculated salt concentration for that 100 years will be constant for each of the 100 years previously. For example, from 1900 to 1999, salt concentration is 200 units. if 1800 - 1899 also has the same concentration as 1900 -1999 has, then we can tell age of the ocean by the formula in argument.
If this is not constant each 100 years, we cannot conclude that age can be calculated.

This assumption is explained in Option A.
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Re: The Earth's rivers constantly carry dissolved salts into its oceans.   [#permalink] 08 Nov 2017, 11:47

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