Calculating Population Growth: 1 & 5 Yrs Ago

AI Thread Summary
The discussion centers on calculating the population of a country given a 2.7% annual growth rate and a current population of 15.2 million. To find the population one year ago, the formula used is based on compound growth: u1 = present population / (1 + growth rate). For five years ago, the same formula applies, adjusted for the number of years. Participants clarify the correct use of the formula and the n-values for accurate calculations. The conversation emphasizes the importance of correctly applying the compound growth formula to determine past populations.
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I am not too sure what to do to answer this question.
Each year for the past 5 years the population of a certain country has increased by a steady rate of 2.7% per annum. The present population is 15.2 million.
a) what was thepopulation 1 yr ago?
b) what was the population 5 years ago?

I forgot what formula to use. Any help and reminders welcome. Thanks
 
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Well, then re-develop that formula using your head (and our hints).
You start out!:smile:
 
I know the normal formula for compound interest is
un = u1 * r^(n-1)
so rearranging that would give u1 = ___(1.027)^5_____
15.2 * 10^6
 
then multiply that answer by (1.027)^(5-1)
 
Not sure what you are doing here. "1 year ago from n=1" is n-value n=0.
Plug that into your equation.
 
thanks I have already worked this out, sorry
 

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