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Re: PS Population (m01q09) [#permalink]
30 Nov 2012, 11:17
Like you, I have a problem with this question, but because of wording. It is fine for the question to ask constant growth rate, but it cannot be ambiguous about base years, which is what it did. For instance, what was the population in 1991 or 1992? it isn't 11% (33%/3) year over year, because that ignores the compounding error that will result. By neglecting to specify that the base interval was 3 years, it falsely implies that the rate of pop. growth is YoY, when an answer like 6400 shows clearly that it is not. To compute YoY and go from 3600 to 4800 over 3 years: 3600(1+growthrate)^3=4800. Then dividing both sides by 3600 yields (1+growthrate)^3=(4/3). We don't have the calculating tools on the GMAT to compute logs and thus it is an unfair question.