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# The Earth s rivers constantly carry dissolved salts into its

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

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25 Aug 2012, 08:03
all the options look competitive here..

negation helps a lot..
this is a very good example to show the importance of technique
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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06 Sep 2012, 00:11
hibloom 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 am confused in B and E . Please clarify .
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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24 Sep 2013, 23:56
Option C is a standard trap in an assumption question.

The answer is just the opposite.

The assumption is that salt in ocean is only built through river deposits.

C would've been correct if it were - There are no salts that leach into the ocean directly from the ocean floor.
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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31 Mar 2014, 15:20
Lets see Why It must be A.

Here the issue is about the validity of scale, which is the level of salt, across various time period. And,here,the time period and the consistency of level in that time period only matter. Now all the factors, which are constantly effecting levels across all time periods will not hurt the consistency of salt levels as all these factors are active across the time period consistently.
As far as E is concern, though biological activities effect the level of salt, they do not hurt the consistency of salt levels across the time period ( for instance: they might reduce the level by x% but across all time period so no variation across levels in different time period).

negation of option A will create variation in the salt levels across different time period, creating an error into the method of measuring time period, accurately. Hence will collapse the argument.
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The Earth s rivers constantly carry dissolved salts into its [#permalink]

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28 Jan 2015, 22:34
jainshruti64 wrote:
hibloom 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 am confused in B and E . Please clarify .

For anyone else confused about B and E, here's my take on these:

(B) At any given time, all the Earth’s rivers have about the same salt levels.
This talks about salt levels in rivers. I am not sure whether I'm technically right, but I figure salt levels is a per unit calculation. I feel, the salt level alone, without knowing the volume of water, cannot determine the total amount of salt in each river.
Example: River A is 10km long and river B is 50km long. Both have salt levels of 100, but I would think river B has more salt because its larger.
Hence salt levels would have no bearing.
(E) None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
Even if some of the salts are used up, E does not say that the people measuring salt levels would be unaware of it. Hence it is possible that the ocean uses 10% of the salt it receives for a certain activity, and the people measuring salt levels already know about it, thus factoring for it in their calculations.
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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07 Feb 2015, 06:46
The argument proposes a method of oceans age calculation using the salt levels in oceans.
A - CORRECT.If yes, the method would be wrong to estimate the number of centuries it takes by taking the last century level as a representative amount. If not, the method can be right.
B - OOS. It's not deal with the salt level comparison among all rivers.
C - OOS.
D - OSS.
E - Whether this happens or not, it can be reflected in the ocean's annual salt level.
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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09 May 2015, 05:05
hibloom 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.

Between A and E.
Negate E.
Few of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
Still we can predict age.Only few salts are used,its not "most".
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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04 Jun 2016, 22:44
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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05 Jun 2016, 21:41
hibloom 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.

Let us do it in a speed-time manner.

The author says that we can find the total age (time) of ocean by the rate at which salt is deposited (speed) from the total salt in the ocean (distance)

So time = distance/speed.

Distance ( amount of salt in ocean currently) is a constant.

But what about speed? We need an assumption that caters to " there have been no unusual rate of salt deposition since the beginning... ie; rate has been somewhat constant"

A perfectly does that. If the rate was huge in the last 100 years, the entire hypothesis behind this is destroyed.

Clarifying confusing options :

B At any given time, all the Earth’s rivers have about the same salt levels.

We are talking about the level of salt in the sea, not in the river. Could be that the salt level in river stays the same but due to summer or something the rate at which they deposit goes down and hence there is drop in the rate they are depositing ( Nien)

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

Biological activities must be occurring since a long long time. This is not an anomaly and has no effect on the outcome of the hypothesis
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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12 Sep 2016, 00:46
The whole thing here is to carefully read the premise. Scientists want to estimate the Earth's maximum age. For that they need to find rate in [salt per year] units.
a) Correct. If for the past hundred years the quantities are unusually large, then the rate will be unusually large too -> ruins the estimation
b) Doesn't matter. Even if all rivers have different salt level, scientists estimate the overall effect, not the individual impact
c) Doesn't matter. Scientist take into consideration the overall change, and they don't care how did that change happened.
d) Out of scope
e) Doesn't matter again. Scientists will observe the overall change, and they don't care how did that change happened
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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12 Oct 2016, 01:06
I know this is an old question. I fell for E too but realized why A is correct:

Conclusion: current salt level / salt deposited in the past century.

suppose 1st year salt level was 10, 2nd year an increase of 5, 3rd year an increase of 5, etc. up to the 100th year, i.e. the conclusion is true only when the ratio remains unchanged which implies that there needs to be a constant increase of salt year on year. This is exactly what (A) states and negating A implies that there is no constant increase of salt year on year.

Does my reasoning make sense? Please correct me if I'm wrong. Hope it helps.
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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12 Oct 2016, 09:33
jainshruti64 wrote:
I am confused in B and E . Please clarify .

Option B would not be correct because it is not necessary that all the rivers of the earth have about the same salt levels at any given time. They can actually have different salt levels. In other words, it is possible that the salt level of one river is different from the salt level of another river.

When I closely think about it, I believe that possible assumption could have been that rivers have actually been carrying approximately the same “quantity” of salt across centuries. In fact, this is pretty much what option A is saying, and hence is the right answer.

The only other option that comes close to this is option E. However, I believe that this is not the correct option because even if this assumption was false it would mean that rivers are carrying salt along with them to the sea and some of that salt is being consumed by biological activity in the oceans. This is actually ok, because even if that was the case, then for every century, the measured salt quantity increase would actually be a “net” of the salt carried by the rivers into the oceans minus the salt consumed by the biological activity in the oceans. Since this is going to be a uniform pattern all through the history, it would in no way give wrong calculation of the maximum age of the oceans of the earth.
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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20 Dec 2016, 22:18
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
* At any given time, all the Earth’s rivers have about the same salt levels.
OOS
* There are salts that leach into the Earth’s oceans directly from the ocean floor.
OOS
* There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
OOS
* None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
If biological process uses the same salt, concentration will definitely fall

The problem is that the argument clearly does not rely on this assumption. Nowhere in the QS does it mention biological activity. It does, however, mention the method that is being used to estimate the age of the earth
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22 Dec 2016, 01:36
I am confused between A & E.
A: The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
Seems correct coz unusually high deposits during the recent century will hamper the calculation which is based on the assumption that each century the amount salt deposited is approximately constant.

E.None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans
The biological activity consumes salt and the amount is not known so it will effect the total quantity of salt left at the end of each century. Total Salt :T Salt consumed by biological activities : B. Salt at the end of century =T-B
this quantity B can be different for different centuries and also, total B for all centuries will also effect the final age calculation Total Salt deposited by rivers in 100years = Total Salt added in oceans in 100 years + Summation of all B over 100 years. Not considering the summation of B will give inaccurate results. Could someone please help me with this
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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06 Jan 2017, 19:01
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 :

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 [#permalink]

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13 Feb 2017, 05:32
doesn't the argument depend on the salt levels being steady over the past hundred years .Both A and B seem like good options ,why its A?
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The Earth s rivers constantly carry dissolved salts into its [#permalink]

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14 Feb 2017, 10:04
giannisch wrote:
doesn't the argument depend on the salt levels being steady over the past hundred years .Both A and B seem like good options ,why its A?

Whether the rivers had same salt levels does not help in arriving at the conclusion. The question is about determining the age of the oceans. Even if the rivers carry salt at different rates into the sea (because of their their different salt concentrations), it is still possible to estimate the age of the ocean by analyzing the rate of rise during last hundred years (assuming that rate of rise in last hundred years represents the average rise from the creation of the ocean, i,e, option A).
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14 Feb 2017, 12:50
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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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink]

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15 Feb 2017, 09:16
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 teh link that connects the premise to the conclusion and the choice that expains the trasnition 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.
Re: The Earth s rivers constantly carry dissolved salts into its   [#permalink] 15 Feb 2017, 09:16

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