Calculating Population Growth: 1 & 5 Yrs Ago

[busted]

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

 

[arildno]

Well, then re-develop that formula using your head (and our hints).
You start out!

 

[busted]

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

 

[busted]

then multiply that answer by (1.027)^(5-1)

 

[arildno]

Not sure what you are doing here. "1 year ago from n=1" is n-value n=0.
Plug that into your equation.

 

[busted]

thanks I have already worked this out, sorry