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

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Vaishali2004

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28 May 2022, 00:22

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Choice A - Even if the rate of deposit of salt was not constant. We could still determine the age by assuming that a constant amount being depotited. That way, we would end up determining higher age of earth than in real. But the conclusion mentions "maximum age" So then wouldn't that still be okay?

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03 Jun 2022, 13:47

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Vaishali2004

Let's say that salt deposits HAVE been unusually high in the past century. If you used this data and mistakenly said that the same thing happened in previous centuries, you'd come up with a time estimate that is too short (as in, you'd think that the water got saltier in a shorter amount of time than it actually took). This would give you a (faulty) maximum age that is too recent. The actual maximum age would be older than your estimate.

So, you need to assume that quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.

That's why (A) is an assumption on which the argument depends.

I hope that helps!

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31 Jul 2022, 06:31

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ttram

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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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01 Aug 2022, 08:26

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Hi avigutman - i selected (A). Quick question on (E).

When i read the argument, essentially the argument is saying : divide the the Green (Numerator) / Blue (Denominator) : You will get the age of the river.

Question on (E).

I did not select (E) because i thought (E) was baked into to the calculations of the green (numerator) to begin with.

Question - is (E) baked into the calculation of
(i) BOTH, the green and the blue
or
(ii) just the blue only
or
(iii) just the green only

As long as (E) is baked into one of these three options - we can eliminate (E) but i was curious

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avigutman

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01 Aug 2022, 19:23

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jabhatta2

We can eliminate (E) because it's "baked in" to both the green and the blue. If it were only "baked in" to one of them, that would be a problem. We need the consistency in order for the calculation to be meaningful, jabhatta2.

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23 Nov 2022, 23:56

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Zatarra

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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 was a difficult choice between a and e.
I eliminated E with the foll. reasoning.
If at the beginning of the last century,the ocean contained x kgs of salt.
If in the last 100 years , 100 kgs of ice was dropped into the ocean by the rivers.
and suppose that in the past 100 yrs 5 kgs of salt was used up by the ocean because of its biological activity.
then 95 kgs was dropped in the last century.
So the level becomes x + 95
still we can find out the age of the ocean by taking 95 kgs as the average increase in 1 century.

But the option does not say in the last 100 years. It could be any of the set of 100 years and can change average salt in that particular slot of 100 years. How does it not affect the amount of the salt/100 years?

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23 Sep 2023, 05:15

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Pre-thinking - We assume that the deposition of salts has been pretty consistent. What if in the last 100 years, the deposition of slats was extremely high say because of industrial activity then the maximum age of Earth's oceans can't be accurately estimated.

(A) The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years. - in line with our pre-thinking.

(B) At any given time, all the Earth’s rivers have about the same salt levels. - Doesn't matter. Irrelevant.

(C) There are salts that leach into the Earth’s oceans directly from the ocean floor. - At best, a weakener.

(D) There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans. - Not an assumption. The argument doesn't say that this is the superior method.

(E) None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. - At best, it's a strengthener. But it is not a necessary condition. Say we negate this - Some (at least 2 - say 2 kgs, for example) of salts ....are used for biological activity...does it even matter? No.

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04 Dec 2023, 09:22

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I got that the answer is A but everyone is ignoring D. I wanted to understand why?
Lets say There is a superior method than the current method to determine the ocean's age, it means that the earlier method that has been used for the same is inaccurate because we have a better method to ensure accuracy?

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16 Dec 2023, 10:19

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anikpait17

I got that the answer is A but everyone is ignoring D. I wanted to understand why?

Lets say There is a superior method than the current method to determine the ocean's age, it means that the earlier method that has been used for the same is inaccurate because we have a better method to ensure accuracy?

Having a "superior" method doesn't necessarily mean that the inferior method is inaccurate -- both methods could be quite accurate, but if one is slightly better, you'd have to call that one superior.

The superior method might also be superior for other reasons aside from accuracy -- maybe that method is easier, faster, or cheaper, for example.

Having a superior method wouldn't necessarily invalidate the argument, so (D) is not a required assumption.

I hope that helps!

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30 Jul 2025, 04:44

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In this question the authors conclusion is that we can predict the maximum age of the oceans , Lets first negate A , if large quantities of salt were dissolved in the past 100 years , We can still get the MAXIMUM age of the oceans , We are not looking for the exact age , we are looking for a maximum. If we were to negate E , and a large quantity of the oceans salt were taken by the ocean for biological process there would be lesser salt in comparison to the actual value , when calculated using this value we would get a value which is lesser than the maximum value , hence the maximum value would be inaccurate . Even option A is a good option and by Option A we would get a inflated maximum value .. I honestly don't know which is better

durgesh79

between A and E...
one of the best ways for CR assumption questions
negate the assumption and the argument should fall apart.

negate E
Some of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
OK.. but if the portion of salt consumed by biological activities has remained constant over the years ... we can still predict the age of the oceans ... the argument doesnt fall apart

negate A
The quantities of dissolved salts deposited by rivers in the Earth’s oceans have been unusually large during the past hundred years.
it means that the rate has not been constant .... we cant predict the age .... agrument falls apart ...

right Option A

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04 Aug 2025, 19:20

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I found that GMAT has such radicicolous reasoning that even AIs cannot respond to its question!!! We should laugh or cry?!

ttram

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 estimated.

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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11 Aug 2025, 15:12

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arjunsathish

It's actually the other way around, as explained in this post: https://gmatclub.com/forum/the-earth-s- ... l#p3025048.

In case that isn't clear, let's say that there are currently 10 million units of dissolved salts in the ocean, and that the oceans were salt-free 10 million years ago. That means the salts were added at an average rate of 1 unit per year.

But maybe the rate was unusually high the past hundred years (say, 10 units per year). If we use that rate along with the current salt level (10 million units), we'll determine that the oceans were salt free only 1 million years ago. In that case, we would greatly underestimate the maximum age of the oceans.

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19 Jan 2026, 10:35

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arguments: rivers carry dissolved salts into ocean.
so consider whatever increment in salt level in ocean and then determine how long would it take to reach this level from zero level

conclusion- we can find the maximum age if oceans accurately

A perfect. they are assuming that salt quantity is somewhat consistent all the time. but if its inconsistent then its not possible to determine. this breaks the conclusion if negated.
B this should be other way around though.
C this is not of great help because it says there are some other ocean that pass on the salt to earths ocean. but thats not the case. even with this we might calculate the age though.
D talks about better method and thats not the case.
E this is not necessary one. even lets say some portion has been used we can still estimate and find the range about maximum and minimum age.

ttram