Critical Reasoning

Since the uniformentarian position is "the present is the key to the past", I believe A would be the answer. Since it is standard to assume rates have stayed constant, then A would be the correct choice.

E doesn't seem to be the answer because they're measuring the increases, which would include calculating how much salt is being absorbed and subtracting that from how much the input is to find out how much of an increase there is.

The other answers are just red herrings.

Initially i voted for E - but thats not correct -

views from other portals -

E is incorrect because the argument is talking about the RESULTING INCREASE, which includes the salts that are used up by biological activity in the oceans or for any other purposes.

B is incorrect because the argument is focusing on the ocean's slat level and not the river's salt level.

I say "A" because if we are estimating billions of years based on 100 years of consecutive data, we must assume the 100 years is not an outlier.
Only A remains.


And OA pposted there is - A

This post was originally made in 2007!!!

This is a great example of why anyone who makes a post needs to include the source and the official answer( hidden by the spoiler). The exception is if you plan to give the official answer within 24 hours (I sometimes don't include the official for a few hours to let the discussion and debate happen). The source should always be posted. Whoever posted this left people hanging for 3 years and counting...

Anyway this one has been discussed by multiple experts at the following link here on BTG: https://www.beatthegmat.com/earth-t66035.html

By the way, looks like A is the answer.

IMO "A"

Since the Argument is about "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 could know the amount of salt deposited by the rivers have not been unusually large, it easy to find out the time it took to have the current salt level in the oceans from No-salt level.

answer choice B considers the extreme case of "amount of dissolved salt carried by rivers was the same at any point of time." but it doesn't say about the deposited amount of the salt in oceans by rivers.


Answer choice C is out of the premises.

Answer "D" out of the premises of argument. as it is not about other Methods.

Answer "E" Though the negation tech helps , you can think about E only if you Know about A i.e primarily one would like to know how much salt was deposited at first place later you can think of E in order to find out age of the oceans . E would have been a good choice if A was not there!

Hope this helps.

Please post the OA

the max age of ocean can be calculated as:

increase in slat levels in ocean in past 100 years

+
n of centuries such increases went on, from a initial time of 0 salt.

so AGE OF EARTH + INCREASE IN SALT IN ONE CENTURY * N CENTURIES = TOT. SALT IN OCEAN NOW

In order for this equation to work we must assume the increase in salt kept the same during the centuries.

So it is ans B

Answer is both A and E!

Reason:

Conclusion: the maximum age of the Earth's oceans can be accurately estimated

Evidence:

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

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

In other words the argument is stating that total age of earth= (final salt-initial salt content)/rate of deposit.

In other words treat this as a distance rate time problem.

The distance here = [Final (higher) concentration - Initial (lower) concentration]
Rate here = rate of deposit

Time here is =age of earth= distance/rate.

The question here is about of maximum age of earth.

let's assume initial salt content =100 grams
Final salt content = 1000 grams.
Change in salt content =900 grams.

Now lets assume following was the data of salt deposited every hundred years -> 100,200,200,400. [negation of assumption]

Age of earth = 900/400= 225 years.

But the real age of earth is 400 years.

Therefore,A is assumed by argument.

E)

Let's assume that salt consumed by biological activities =100

Final salt reading =900

Change in salt content =(900-100)=800

Now lets assume following was the data of salt deposited every hundred years -> 100,100,100,100,100,100,100,100,100

Now age of earth = 800/100= 800 years but actually the age of the earth was 900 years.

Remember you can't yourself assume "as in the thread posted by GMATGuruNY@ https://www.beatthegmat.com/earth-t66035.html" that the salt used by biological species was very limited.

Even if you did,the maximum possible age of earth would still be less than real age of earth.

For eg The question is DS is "is x<=0.75"

1) 0.74<x<0.7510
2) 0.74<x<0.750001

In this the answer would be E " 1) x could be 0.74 (true) x could be 0.7509 (false) Insufficient 2) x =0.75 (true) or x=0.7500009(false) and same with C"

You can't say x is only slightly greater than 0.75 in 1 or 2.This is WRONG.



This too is assumed by the argument

Therefore,as such,this question is wrong,according to me.Both A and E are assumed by the question.

OA is A

lol!!

E

The method to compute the earth's oceans age relies on an increase in salt levels every century, but, if the biological activity in the ocean uses up the salts in a particular century, it is quit likely that the levels of salt in a particular century could be lower than the levels in the previous century and the method to determine the age could be inaccurate

Some expert please respond to this.

Thanks
Mankey

Expert has already responded to this. Had missed it. Sorry.

Mankey