Question

The annual rate of growth in population of a certain city is 8%. If its present population is 196830, what it was 3 years ago?

Answer 1

$$\begin{gathered} \mathrm{Population}\mathrm{after}\mathrm{three}\mathrm{years}=\mathrm{P}{\left(1+\frac{\mathrm{R}}{100}\right)}^{\mathrm{n}} \\ 196,830=\mathrm{P}{\left(1+\frac{8}{100}\right)}^3 \\ 196,830=\mathrm{P}{\left(1.08\right)}^3 \\ \mathrm{P}=\frac{196,830}{1.259712} \\ =156,250 \\ \mathrm{Thus},\mathrm{the}\mathrm{population}\mathrm{three}\mathrm{years}\mathrm{ago}\mathrm{was}156,250. \end{gathered}$$