The percentage difference is the difference divided by the original times 100. eg percentage difference between 80 and 90 = (90-80) / 80 x 100 which is 10 / 80 x 100 which is 12.5 In other words it has increased by 12.5 percent.

Adding four percent to a number is the same as multiplying the number by 1.04. In this instance, 1.04 x 80 = 83.2. therefore, 80 increased by 4 percent is equal to 83.2.