If the population was 40,000 at the beginning of 2009, at the end of 2009 it has increased by 10% and became 44,000.
By the same way, at the end of 2010, it became [tex]44000 + \frac{44000*10}{100} = 48400[/tex]
At the end of 2011, the population was [tex]48400 + \frac{48400 * 10}{100} = 53240[/tex]