The annual number of burglaries in a town rose by 50% in 2012 and fell by 10% in 2013. Hence the total number of burglaries increased by 40% over the two­ year period. What is the mistaken assumption here?

Why is that assumption incorrect?

By what percent has the number of burglaries actually changed in the two-year period? show calculation

By what percent would the crime have to decrease in the second year in order for the change over the two-year period to actually be a 40% increase? Round to nearest 10th percent (ex-decimal .05873 is 5.873% to one decimal is 5.9%) show calculation