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# Scientists have determined that Radon - a colorless,

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10 Feb 2013, 23:14
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Scientists have determined that Radon - a colorless, odorless, and tasteless gas - is unstable because of its radioactive nature and continuously decays into Progeny. Since it has been proven that there was no Progeny at the time of earth’s formation, one can accurately estimate earth’s age by determining the increase in Progeny in earth’s atmosphere over the last 200 years and using it to determine how many years it would have taken to reach current levels of Progeny.

The answer to which of the following questions would be most important in determining whether using the method would help in achieving the stated objective?

A. Whether the rate of decay of Radon into Progeny is different during day time and night time?
B. Whether Progeny is stable or gets converted into some other gas at constant rate?
C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases?
D. Whether there are methods, better than the method given, to estimate the earth’s age?
E. Whether amount of Radon or Progeny varies from region to region?
[Reveal] Spoiler: OA

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Last edited by egmat on 11 Feb 2013, 19:45, edited 1 time in total.
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10 Feb 2013, 23:15
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Hi,

Please find below the official solution:

Understanding the Argument

Conclusion
Earth’s age can be estimated by:
• determining the increase in Progeny in earth’s atmosphere over the last 200 years and
• using it to determine how many years it would have taken to reach current levels of Progeny

Premises
1. Radon gas is unstable because of its radioactive nature and continuously decays into Progeny
2. There was no Progeny at the time of earth’s formation

Prethinking

What is the fundamental assumption?

While making his claim, the author assumes that the rate of change of Progeny over the past 200 years is representative of the rate of change of Progeny over the course of history of earth. If this is not the case, i.e. if the rate of change today is much lower or much higher than what it used to be in the past, then the estimates would either be too high or too low.
You may go to the analysis of answer choices if the above makes sense to you. Otherwise, read below if you need more explanation.

Detailed description of how to Prethink

Prethinking in the given question is extremely difficulty unless one has a basic understanding of data representativeness, which basically means that if a sample data is used to make predictions about a population, then the sample data must be representative of the population data. (fundamental assumption)

Since this is pretty technical definition, let’s take an example to understand this. At the end of this example, we will provide a weaken question where the same principle has been used with a twist in a weaken problem.

Suppose you are given a task to estimate the population of a city. Suppose the city has 100 residential blocks. One way to find out the population can be to go to each and every block and count the number of people in each of the blocks and then totaling them to find the total population of the city.

Another way, and a much easier way is estimate the population rather than calculating the same. To do the same you go to, say, 4 residential blocks and find out their populations and calculate the sum of populations in these residential blocks.
Then, the total population of the city can be estimated by multiplying 25 (i.e. 100/4) with the sum of population in these 4 residential blocks.

Do you think this method will work? What if you chose the 4 residential blocks which happen to be the most populous residential blocks in the city? Would you get a correct estimate of the population in such a case?

The answer is No. You would get an estimate which is much higher than the actual population. Similarly, if you chose the least four populous residential blocks, you would get an estimate which is much below the actual population.

Therefore, to get a correct estimate of the population of the city, you must select 4 residential blocks which have near average populations of all the residential blocks. And if you choose residential blocks in such a way, your sample data (i.e. 4 residential blocks) would be a correct representation of the population and the sample can be called as representative of the population.

Now, let’s apply the same knowledge in the given question. If we are using the increase in the amount of Progeny in the last 200 years to estimate the Earth’s age, then that increase should be representative of the increase that happens every 200 years. This is the assumption required. If the increase in Progeny in the last 200 years is significantly different from such increases in the past, then we would have an incorrect estimate. Therefore, one thing we need to evaluate is whether the increase in Progeny in the last 200 years is representative of such increases since the beginning of the earth.

(A weaken question which uses the same understanding: gasoline-cars-in-papula-country-147427.html)

A. Whether the rate of decay of Radon into Progeny is different during day time and night time? – This is irrelevant. Even if the rates are different during day time from night time, it doesn’t impact the estimate. Incorrect.

B. Whether Progeny is stable or gets converted into some other gas at constant rate? – There are two cases to consider in this option statement:
i. Progeny is stable: In this case, the estimate should work perfectly fine.
ii. Progeny gets converted into some other gas at constant rate –
Since this conversion happens both during the last 200 years and the time since the formation of earth, it doesn’t distorts the estimate. This is because such constant conversion impact the increase in gas in the last 200 years in the same proportion as the increase in gas in the time since the formation of earth. Thus, an estimate of the earth’s age, which would be calculated as below, will not be affected.
Earth’s Age: Total Amount of Progeny in the atmosphere currently*200/Increase in the amount of Progeny in the atmosphere in the last 200 years
Incorrect.

C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases? – As we discussed in the Pre-thinking stage, if this given option statement is true, last 200 years of data regarding increase in progeny would not be representative of the time since the formation of Earth. Therefore, we need to find out the answer to this question to know whether the data of increase of Progeny in the last 200 years can be used to estimate the Eath’s age. Correct.

D. Whether there are methods, better than the method given, to estimate the earth’s age? – We are not concerned with an answer to this. Incorrect.

E. Whether amount of Radon or Progeny varies from region to region? – Since we considering the earth’s atmosphere as a whole, even if Progeny varies from region to region, it doesn’t impact the estimate because we are taking into account all the regions. Incorrect.

Hope this helps

Thanks,
Chiranjeev
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Last edited by egmat on 22 Feb 2013, 00:09, edited 1 time in total.
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11 Feb 2013, 01:22
According to me the OA should be B

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11 Feb 2013, 03:15
egmat wrote:
Scientists have determined that Radon - a colorless, odorless, and tasteless gas - is unstable because of its radioactive nature and continuously decays into Progeny. Since it has been proven that there was no Progeny at the time of earth’s formation, one can accurately estimate earth’s age by determining the increase in Progeny in earth’s atmosphere over the last 200 years and using it to determine how many years it would have taken to reach current levels of Progeny.

The answer to which of the following questions would be most important in determining whether using the method would help in achieving the stated objective?

A. Whether the rate of decay of Radon into Progeny is different during day time and night time?
B. Whether Progeny is stable or gets converted into some other gas at constant rate?
C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases?
D. Whether there are methods, better than the method given, to estimate the earth’s age?
E. Whether amount of Radon or Progeny varies from region to region?

OA will be posted on Tuesday!!

Facts:
* Radon (colorless,odorless and tasteless gas) is unstable because of its radioactive nature and consinuously decays into Progeny
* There was no Progeny at the time of earth's formation
Method :
Determining the increase in Progeny in earth’s atmosphere over the last 200 years and using it to determine how many years it would have taken to reach current levels of Progeny.
Stated objective :
Estimate earth's age
IMO
A. Clearly irrelevant
B. CORRECT, Whether Progeny is stable or gets converted into some other gas at constant rate will help us to know if the method is accurate. If the answer to this question is No then how can we determine the increase in Progeny in earth's atmosphere if Progeny is unstable adn therefore we could NOT estimate the number of years it would have taken to reach current levels of Progeny.
C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases is IRRELEVANT since Randon is an example of a gas who undergoes its radioactivity nature but consinously decays into Progeny according to the first fact.
D. INCORRECT , we are requiered to evaluate the method stated Vs the stated objective.
E. Irrelevant since we are concerned with earth's atmosphere .....
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11 Feb 2013, 05:52
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Premise :- Radon decays into Progney, by measuring the increase in progeny over last 200 years age of earth can be determined.

assumption :- the sample data is representative enough, means the average increase in progeny over its lifetime would be the same as the increase in past 200 years.

POE :-

A :- Different decay rate during day time/night time :- since we are concerned with the aggregate increase over the 200 year period this is not correct.
B :- Whether Progney is stable or converted into another gas @constant rate :- This option states that for both the extreme spectrums of a Yes/No answer, you will be able to determine the age of earth. If Progeny is stable then by directly measuring the increase in Progney or if it gets converted into another gas then by measuring the increase in another gas. The answer choice does not fluctuate to extremes and hence is not the correct answer.
C :- changes in atmosphere over last century :- A No answer to the question will state that the decay is constant and the 200 year sample is representative enough. A yes answer to the question will state that the 200 year sample is not representative enough, and hence is the correct option.
D :- other methods :- OFS
E :- Amount of progeny varies from region to region :- similar to option A, this option also segregates decay by region but our scope is for the entire earths atmosphere.

IMO :- C
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11 Feb 2013, 08:21
My analysis

Firstly this is an evaluate the argument type question.

Facts/Premise - Radon is a gas which decays and becomes Progeny.
There was not Progeny when earth was formed.
Because of this reason earth' age can be accurately estimated. How by calculating the increase in Progeny and then determining in how many years this increase happened.

Underlying fact or assumption is - Progeny does not decay or converts into something else because the total amount of progeny is important for calculating the age.

A) OFS the rate of day and night is not relevant
B) Looks relevant and very close to our assumption. Park it for variance test
C) Can be relevant. park it for final analysis.
D) Completely OFS.
E)No relevant the argument is not talking about regional changes.

Now lets analyze C and D

B) moved to one extreme Progeny is not converted to any other gas - conclusion is validated. The proposed method would work.
Other extreme - Progeny is converted to some other gas, but the method is measuring only progeny hence it will miss out on the converted Progeny. Invalidated
B is the correct choice ( but lets look at C too)

C) Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases?

Yes there have been changes - Does not impact the argument, this increase will be factored in the calculation. As for Progeny it is not mentioned if it is also decaying.
No there have not been changes - Again no impact.

So B is the correct choice. Waiting for the explanation from E-gmat.

egmat wrote:
Scientists have determined that Radon - a colorless, odorless, and tasteless gas - is unstable because of its radioactive nature and continuously decays into Progeny. Since it has been proven that there was no Progeny at the time of earth’s formation, one can accurately estimate earth’s age by determining the increase in Progeny in earth’s atmosphere over the last 200 years and using it to determine how many years it would have taken to reach current levels of Progeny.

The answer to which of the following questions would be most important in determining whether using the method would help in achieving the stated objective?

A. Whether the rate of decay of Radon into Progeny is different during day time and night time?
B. Whether Progeny is stable or gets converted into some other gas at constant rate?
C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases?
D. Whether there are methods, better than the method given, to estimate the earth’s age?
E. Whether amount of Radon or Progeny varies from region to region?

OA will be posted on Tuesday!!
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11 Feb 2013, 13:00
imho, B (Whether Progeny is stable... ) is not correct, since in the q. stem we are said that that Radon - a colorless, odorless, and tasteless gas - is indeed unstable

I choose answ C
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12 Feb 2013, 04:15
I think this question is the replica of an official question.
Strange not much of discussion......

Conclusion: Earth's age can be determined by tracing the development of progenies.
In argument its mentioned that earths age can be found accurately by interpolation. That means the method has some kind of proportionality with the age of earth. Hence option choice B fits the gap.

C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases?
<<<<<<<<<<I think option C is a trap, consider the situation , if radioactivity decay has increased but a formula can be devised to calculate the relation between earths age and increase in radioactivity.....>>>>>>

Archit
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12 Feb 2013, 04:16
No post from Sarvana test prep<<<<>>>>>>>>
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14 Feb 2013, 17:59
Hi All,

The Official Answer for this question is Option C.

Dinesh2APR - You are right

Thanks,
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15 Feb 2013, 07:01
Dinesh2Apr wrote:
Premise :- Radon decays into Progney, by measuring the increase in progeny over last 200 years age of earth can be determined.

assumption :- the sample data is representative enough, means the average increase in progeny over its lifetime would be the same as the increase in past 200 years.

POE :-

A :- Different decay rate during day time/night time :- since we are concerned with the aggregate increase over the 200 year period this is not correct.
B :- Whether Progney is stable or converted into another gas @constant rate :- This option states that for both the extreme spectrums of a Yes/No answer, you will be able to determine the age of earth. If Progeny is stable then by directly measuring the increase in Progney or if it gets converted into another gas then by measuring the increase in another gas. The answer choice does not fluctuate to extremes and hence is not the correct answer.
C :- changes in atmosphere over last century :- A No answer to the question will state that the decay is constant and the 200 year sample is representative enough. A yes answer to the question will state that the 200 year sample is not representative enough, and hence is the correct option.
D :- other methods :- OFS
E :- Amount of progeny varies from region to region :- similar to option A, this option also segregates decay by region but our scope is for the entire earths atmosphere.

IMO :- C

HI Dinesh...
I have a doubt , when you say that Assumption is "Sample is representative i.e. it can be interpolated to get a correct idea of the earth's age"
I also thought of same assumption and selected B....Because i feel that B mentions two every important words that can bring contrast when answered Yes or No....
They are:-
1. Stable and 2. Constant rate...
If something does not changes at a constant rate how can you predict the age using the sample data...Another One is Stable, If its not stable than it is difficult to predict an accurate age of the substance.
I agree that Option C mentions something which is valid, but i feel that option B presents stronger reasoning than C.

Can you explain why did you not consider choosing B.

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15 Feb 2013, 08:39
Archit143 wrote:
Dinesh2Apr wrote:
Premise :- Radon decays into Progney, by measuring the increase in progeny over last 200 years age of earth can be determined.

assumption :- the sample data is representative enough, means the average increase in progeny over its lifetime would be the same as the increase in past 200 years.

POE :-

A :- Different decay rate during day time/night time :- since we are concerned with the aggregate increase over the 200 year period this is not correct.
B :- Whether Progney is stable or converted into another gas @constant rate :- This option states that for both the extreme spectrums of a Yes/No answer, you will be able to determine the age of earth. If Progeny is stable then by directly measuring the increase in Progney or if it gets converted into another gas then by measuring the increase in another gas. The answer choice does not fluctuate to extremes and hence is not the correct answer.
C :- changes in atmosphere over last century :- A No answer to the question will state that the decay is constant and the 200 year sample is representative enough. A yes answer to the question will state that the 200 year sample is not representative enough, and hence is the correct option.
D :- other methods :- OFS
E :- Amount of progeny varies from region to region :- similar to option A, this option also segregates decay by region but our scope is for the entire earths atmosphere.

IMO :- C

HI Dinesh...
I have a doubt , when you say that Assumption is "Sample is representative i.e. it can be interpolated to get a correct idea of the earth's age"
I also thought of same assumption and selected B....Because i feel that B mentions two every important words that can bring contrast when answered Yes or No....
They are:-
1. Stable and 2. Constant rate...
If something does not changes at a constant rate how can you predict the age using the sample data...Another One is Stable, If its not stable than it is difficult to predict an accurate age of the substance.
I agree that Option C mentions something which is valid, but i feel that option B presents stronger reasoning than C.

Can you explain why did you not consider choosing B.

Archit

Hello Archit,

Below is my analysis of option B

Option B:- Whether Progeny is stable or gets converted into some other gas at constant rate.

This choice gives you 2 options for Progeny, for these answer choices the Yes/No will be choosing 1 option over other.

suboption B.1 :- Progeny is stable
Now if Progeny is stable, means Progeny will remain there and not vaporize or change into another form. So you can measure Progeny over the past 200 years and get to the conclusion. This option does not break the conclusion.

suboption B.2 :- Progeny gets converted into other gas at constant rate
In this option since the rate of conversion is constant, you can still devise a formula to reach the conclusion by measuring the amount of Progeny left(or by measuring the change in quantity of the other gas) and factoring for the constant of proportionality. This option also does not break the conclusion.

since neither of the options breaks your conclusion, option B is not the correct answer.

Had this option not included the 'constant rate', this option choice might have been a good contender.

Hope this helps !
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15 Feb 2013, 11:09
I have little different view
B1:- Progeny is stable
Consider :- Progeny is unstable
That means its not possible to derive the age of the earth.
Consider:- Progeny is unstable
That means its possible to derive the age of earth.
We are getting two polar opposite answer.

Now,
B2 :- Rate of conversion is constant
Consider:- Rate of conversion is not constant
Hence its not possible to derive a formula for interpolation.
Consider:- Rate of conversion is constant
Hence its possible to derive a formula for interpolation.
So if you go by your break up we will get two polar opposite answers.

Even if we take them together

But yes agree to a point the analysis of this one is bit complicated and rather option C is simple, hence can be considered a better answer.
But if go by logic i think both equally hold good chance.

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22 Feb 2013, 00:26
Hi Guys,

The official solution with explanation has been posted. Check it out. Apologies for the delays.

Thanks,
Chiranjeev
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22 Feb 2013, 03:12
egmat wrote:
Hi Guys,

The official solution with explanation has been posted. Check it out. Apologies for the delays.

Thanks,
Chiranjeev

hi Chiranjeev
I think this is an official example from gmac......can you pls post the link to official question...just want to compare......

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22 Feb 2013, 03:19
Archit143 wrote:
egmat wrote:
Hi Guys,

The official solution with explanation has been posted. Check it out. Apologies for the delays.

Thanks,
Chiranjeev

hi Chiranjeev
I think this is an official example from gmac......can you pls post the link to official question...just want to compare......

Archit

Hi Archit,

This is not an official question from GMAC. This one is from the e-GMAT kitchen. All questions posted by us here are created just for the forum. They are not even a part of the course.
Thanks,
Chiranjeev
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25 Feb 2013, 13:20
egmat wrote:
Archit143 wrote:
egmat wrote:
Hi Guys,

The official solution with explanation has been posted. Check it out. Apologies for the delays.

Thanks,
Chiranjeev

hi Chiranjeev
I think this is an official example from gmac......can you pls post the link to official question...just want to compare......

Archit

Hi Archit,

This is not an official question from GMAC. This one is from the e-GMAT kitchen. All questions posted by us here are created just for the forum. They are not even a part of the course.
Thanks,
Chiranjeev

hi chiranjeev

With all regards to you, I have seen a similar question in an official source......i ll have to look for it exhaustively...but i m 100 % sure that i have seen one...no issues once i find i ll post...
by the way good work chiranjeev..Many claimed experts crumbling.....hahah. its 2 down ..lets see who is the next.

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02 Jul 2015, 10:58
this is similar to the one about rivers filling ocean with salts or something like that. An OG ques
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14 Jul 2016, 10:12
Scientists have determined that Radon - a colorless, odorless, and tasteless gas - is unstable because of its radioactive nature and continuously decays into Progeny. Since it has been proven that there was no Progeny at the time of earth’s formation, one can accurately estimate earth’s age by determining the increase in Progeny in earth’s atmosphere over the last 200 years and using it to determine how many years it would have taken to reach current levels of Progeny.

The answer to which of the following questions would be most important in determining whether using the method would help in achieving the stated objective?

A. Whether the rate of decay of Radon into Progeny is different during day time and night time?
B. Whether Progeny is stable or gets converted into some other gas at constant rate?
C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases? - As highlighted in the argument, the fact that the test would study the change in atmosphere over the past 200 years makes this the correct ans.
D. Whether there are methods, better than the method given, to estimate the earth’s age?
E. Whether amount of Radon or Progeny varies from region to region?
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Re: Scientists have determined that Radon - a colorless,   [#permalink] 14 Jul 2016, 10:12
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