arithmetic - the population of a town increases by 10 per annum for two years then decreases by 10 per annum for the next two years if the population of the town four year ago was 10000 what would it be today - skillgun

Increase of population = (100+10)% = 110% = 1.1
Reduction of population = (100 -10)% = 90% = 0.9
Total effect = 1.1 X 1.1 X 0.9 X 0.9 = 0.9801,
Population = 10000 X 0.9801 = 9801