bac-s-maths 2013 Q4b

bac-s-maths · France · metropole 5 marks Matrices Matrix Power Computation and Application
(For candidates who have followed the specialization course) We study the population of an imaginary region. On January 1, 2013, this region had 250,000 inhabitants, of which $70 \%$ lived in the countryside and $30 \%$ in the city. Examination of statistical data collected over several years leads to the choice of modelling the population evolution for the coming years as follows:
  • the total population is globally constant,
  • each year, $5 \%$ of those living in the city decide to move to the countryside and $1 \%$ of those living in the countryside choose to move to the city.
For every natural number $n$, we denote $v _ { n }$ the number of inhabitants of this region living in the city on January 1 of the year $(2013 + n)$ and $c _ { n }$ the number of those living in the countryside on the same date.
  1. For every natural number $n$, express $v _ { n + 1 }$ and $c _ { n + 1 }$ as functions of $v _ { n }$ and $c _ { n }$.
  2. Let the matrix $A = \left( \begin{array} { l l } 0{,}95 & 0{,}01 \\ 0{,}05 & 0{,}99 \end{array} \right)$.
\textbf{(For candidates who have followed the specialization course)}\\
We study the population of an imaginary region. On January 1, 2013, this region had 250,000 inhabitants, of which $70 \%$ lived in the countryside and $30 \%$ in the city.\\
Examination of statistical data collected over several years leads to the choice of modelling the population evolution for the coming years as follows:
\begin{itemize}
  \item the total population is globally constant,
  \item each year, $5 \%$ of those living in the city decide to move to the countryside and $1 \%$ of those living in the countryside choose to move to the city.
\end{itemize}
For every natural number $n$, we denote $v _ { n }$ the number of inhabitants of this region living in the city on January 1 of the year $(2013 + n)$ and $c _ { n }$ the number of those living in the countryside on the same date.

\begin{enumerate}
  \item For every natural number $n$, express $v _ { n + 1 }$ and $c _ { n + 1 }$ as functions of $v _ { n }$ and $c _ { n }$.
  \item Let the matrix $A = \left( \begin{array} { l l } 0{,}95 & 0{,}01 \\ 0{,}05 & 0{,}99 \end{array} \right)$.
\end{enumerate}