To find the percentage difference between 100 and 19, we first need to calculate the absolute difference between the two numbers. The absolute difference is simply the positive difference between the two numbers, regardless of which number is larger.

In this case, the absolute difference between 100 and 19 is 81 (100 - 19 = 81).

Next, we need to calculate the relative difference between the two numbers. The relative difference is the absolute difference expressed as a percentage of the average of the two numbers.

To find the average of 100 and 19, we add the two numbers together and divide by 2:

(100 + 19) / 2 = 59.5

So the relative difference between 100 and 19 is:

(81 / 59.5) x 100% = 136.13%

Therefore, the percentage difference between 100 and 19 is 136.13%. This means that 19 is 136.13% less than 100, or that 100 is 136.13% more than 19.