The yearly changes in the population of a town for four consecutive years were, respectively, 25% increase, 25% increase, 25% decrease, and 25% decrease. what is the net present decrease over the four years, rounded to the nearest percent?

The net change is a 12.11% decrease.

To see what is going on in this problem, we should write an equation. Let's start by using P to represent the total population.

P x 1.25 x 12.5 x 0.75 x 0.75 = 0.8789

For the increases, we multiplied by 1.25. For the decreases, we multiplied by 0.75.

The final result is the P gets multiplied by 0.8789. In other words it is made smaller by 12.11%.  100% - 87.89% = 12.11%