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Average Age

by 800GMAT » Thu Jun 07, 2007 8:15 pm
Over the last 10 years, there has been a dramatic increase in the number of people over the age of 65 living in this region. This is evident from the fact that during this time the average age of people living in this region has increased from approximately 52 to 57 years.

Which one of the following, if true, would most strengthen the argument?

(A) The number of people in the region under the age of 18 has increased over the last 10 years

(B) The birthrate for the region decreased significantly over the last 10 years

(C) The total number of people living in the region has decreased in the last 10 years

(D) The number of people who have moved into the region in the last 10 years is greater than the number of those who moved out

(E) The average age for people in this region is higher than that of people in surrounding areas

Pls include your reasoning..Thnx
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by plodder_81 » Thu Jun 07, 2007 8:39 pm
Ans is B. To make the conclusion evident from the average age increase, we should make sure average age increase is not due to any other factor for e.g influx of aged population from other region or increase in birth rate .


(A) The number of people in the region under the age of 18 has increased over the last 10 years - This may not support but oppose the conclusion as it pertains to an increase in younger generation.

(B) The birthrate for the region decreased significantly over the last 10 years . This adds to the conclusion we can remove any doubts about significant increase in birthrate thus affecting the average age increase.

(C) The total number of people living in the region has decreased in the last 10 years . This negates the conclusion as it may explain the average ag increase due to a decrease in younger aged population.

(D) The number of people who have moved into the region in the last 10 years is greater than the number of those who moved out . This weakens the conclusion as the increase in age might be explained due to an influx of aged population but not who have been living there.

(E) The average age for people in this region is higher than that of people in surrounding areas - We are not concerned about the relative difference of age in the surrouding areas.


Please let me know if this is the correct answer . My explanation might include some fallacy .

-plodder
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by rocky » Thu Jun 07, 2007 10:18 pm
I Think the answer should be A .The reasoning is as follows:

c,d and e doesn't have any direct relevance with the average increase.
From A and B

According to B, the birth rate has decreased and this can lead to increase in average age as there will be relatively less people with lower ages (than 65)since less people will be at lower ages and hence leading to the higher average relative to previous decades.

A sound good as ,if the there is increase in below 18, then the average can increase only if(probability) there is a increase in the number of people above 65

We think in term of which case gives higher probability of people having age above 65.

This is my view

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by f2001290 » Fri Jun 08, 2007 5:46 am
Same as plodder_81 - B
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by isisalaska » Fri Jun 08, 2007 7:58 am
Right answer is B, if there are not more births the population ahe. Hence, the population age has increased becasue of lack of births.
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by 800GMAT » Fri Jun 08, 2007 10:18 pm
The OA is A...
If the age increase went from 52 to 57 and we are trying to show that people of age 65 increased we have to show that the number of people below age 52 did not decrease because if that was the case then the change in average age was not necessarily caused by an increase in people over age 65
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by [email protected] » Wed Jul 22, 2009 10:31 pm
Would have gone for B at the first go... But now I see that A makes more sense..

If the number of ppl below the age of 18 has increased and still the average has risen then it means people in the higher age groups are increasing..

B would not be the answer because if the birth rate has decreased in the previous 10 years then the increase in average would be attributed to the fact that the percentage of younger population has decreased irrespective of what happened to the older ppl..
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by Domnu » Thu Jul 23, 2009 5:01 pm
Actually, the answer should be A. Here's why:

If the birthrate decreases, the overall mean age increases. By how much? We don't know... but it's possible that if the birthrate is 0% (oh noes) then the mean age could have increased from 52 to 57 and everybody could just be under 60 years old.

If there are many people under 18 on the other hand, there have to be older people to cause the increase.
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Re: Average Age

by dtweah » Sun Jul 26, 2009 11:45 pm
800GMAT wrote:Over the last 10 years, there has been a dramatic increase in the number of people over the age of 65 living in this region. This is evident from the fact that during this time the average age of people living in this region has increased from approximately 52 to 57 years.

Which one of the following, if true, would most strengthen the argument?

(A) The number of people in the region under the age of 18 has increased over the last 10 years

(B) The birthrate for the region decreased significantly over the last 10 years

(C) The total number of people living in the region has decreased in the last 10 years

(D) The number of people who have moved into the region in the last 10 years is greater than the number of those who moved out

(E) The average age for people in this region is higher than that of people in surrounding areas

Pls include your reasoning..Thnx
A b/c the average age only rose from 52 to 57( 5 points), and not closer to 65. This drag can be attributed to increase in the number of under 18. This means that the number of people under 18 is greater than the number of people over 65.

B is eliminated b/c it makes no specific reference to any particular age group: Under 18 or over 65, but speak generally of birth rate.
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A

by sumank8216 » Mon Jul 27, 2009 7:13 am
A.

AVG = (65<)* L + 65*M/ L+M

so L has increased in past 10 years.Corresponding numerotor wont increase that much as it just 18, which is very less.And denominator has increased . So M has to increase to increase to increase the total sum of age and that would increase the average.
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by micheal_kr » Sun May 15, 2016 11:39 pm
I would go with option A as the correct option
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