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Population Growth Problem FLASHCARDS

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rockrock
 Post subject: Population Growth Problem FLASHCARDS
 Post Posted: Mon Jul 26, 2010 5:02 pm 
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Course Students


Posts: 38
Is the statement sufficient?

A group of rabbits multipllies at a constant rate. By what factor does its population increase every day?

(1) The population grows from 200 to 5,000 in one week.

I know we aren't supposed to calculate the answer, but I have a question about how it IS calculated.

The solution: In 7 days the population increases by a factor of 5000/200 = 25. In one day it increases by a factor of 7th root of 25.

Why do we take the 7th root?
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gpinder77
 Post subject: Re: Population Growth Problem FLASHCARDS
 Post Posted: Tue Jul 27, 2010 6:05 pm 
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Students


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rockrock wrote:
Is the statement sufficient?

A group of rabbits multipllies at a constant rate. By what factor does its population increase every day?

(1) The population grows from 200 to 5,000 in one week.

I know we aren't supposed to calculate the answer, but I have a question about how it IS calculated.

The solution: In 7 days the population increases by a factor of 5000/200 = 25. In one day it increases by a factor of 7th root of 25.

Why do we take the 7th root?


hmm.....not sure why are calculating the nth roots but.....i would would it like this.

5000-200 = week growth/7 = daily growth.

so the statement is sufficient to answer the question
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tim
 Post subject: Re: Population Growth Problem FLASHCARDS
 Post Posted: Sat Sep 04, 2010 10:02 pm 
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ManhattanGMAT Staff


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Location: Southwest Airlines, seat 21C
um, no. when the population grows or multiplies at a constant rate, you divide the final by the initial then take the nth root, as the original poster said. but yes you would never actually calculate the 7th root of 25 on the GMAT; just knowing it could be done makes the information sufficient..

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Tim Sanders
Manhattan GMAT Instructor
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