Question

Over the course of a year, the population of rats in Memphis increased from 350000 to 406000.

Answer 1

It is very important to look at all the details that are already given in the question. Only then the problem should be started for solving.
Initial population of Memphis = 350000
population of Memphis after 1 year = 406000
Then
Increase in population of Memphis in a year = 406000 - 350000
                                                                       = 56000
Then
Percentage increase in the
population of Memphis in a year = (56000/350000) * 100
                                                    = (56 * 10)/35
                                                    = 560/35
                                                    = 16 percent
So there is a 16% increase in the population of Memphis in a year.