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#### At the beginning of 2010, 60% of the population of Town X li

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 Post subject: At the beginning of 2010, 60% of the population of Town X li  Posted: Thu Jun 14, 2012 11:20 am
 Students

Posts: 26
 Hi,This is a question from my CAT2:At the beginning of 2010, 60% of the population of Town X lived in the south and the rest lived in the north. During 2010, the population of Town X grew by 5.5%. If the population in the south grew by 4.5%, by how much did the population in the north grow?(A) 1%(B) 3.5%(C) 6.5%(D) 7%(E) 13.75%I had the same approach with the alternative way of the explanation (choose total to be 100, or 1000), but I didn't choose the total number of people, I chose the total percentage of the population to be 100%.Before: 100%South = 60%North = 40%After: 105.5%South = 60% + 60% x 4.5% = 62.7%Therefore North = 105.5 - 62.7 = 42.8%So North increase = 42.8 - 40 = 2.8%.Now I don't see any choice to be 2.8%. I re-read the question and it states "by how much did the population in the north grow?". Therefore the answer is the population in the north grew by 2.8%. I didn't know that the question asks that 2.8% is how much of 40%, which the answer is 7% (D).Should the question be more specific, to avoid confusion? I think if the question asks for "percent increase" then it would be clearer. Thanks!-C

 Post subject: Re: At the beginning of 2010, 60% of the population of Town X li  Posted: Sun Jun 17, 2012 10:26 pm
 ManhattanGMAT Staff

Posts: 2390
 catennacio wrote:Hi,This is a question from my CAT2:At the beginning of 2010, 60% of the population of Town X lived in the south and the rest lived in the north. During 2010, the population of Town X grew by 5.5%. If the population in the south grew by 4.5%, by how much did the population in the north grow?(A) 1%(B) 3.5%(C) 6.5%(D) 7%(E) 13.75%I had the same approach with the alternative way of the explanation (choose total to be 100, or 1000), but I didn't choose the total number of people, I chose the total percentage of the population to be 100%.Before: 100%South = 60%North = 40%After: 105.5%South = 60% + 60% x 4.5% = 62.7%Therefore North = 105.5 - 62.7 = 42.8%So North increase = 42.8 - 40 = 2.8%.Now I don't see any choice to be 2.8%. I re-read the question and it states "by how much did the population in the north grow?". Therefore the answer is the population in the north grew by 2.8%. I didn't know that the question asks that 2.8% is how much of 40%, which the answer is 7% (D).Should the question be more specific, to avoid confusion? I think if the question asks for "percent increase" then it would be clearer. Thanks!-CYou were close! And yeah, I understand your comment, but when all your answers are percents you have to assume that you are dealing with percents.You found that the north grew from 40% to 42.8%. Remember, percent change is the difference over the original amount. Thus, the change of 2.8% divided by the original amount of 40% is like 28/400 or 7%.I hope that this helped! :-) _________________Jamie NelsonManhattanGMAT Instructor

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