What is the difference between percent increase and percent decrease?

The percent increase is given by

(New Value - Old Value)/ Old Value

The pecent decrease is given by

(Old Value - New Value)/Old Value

For instance, if something increased from 8 to 10, the  percent increase is just

(10 - 8)/ 8 = 2/8 = 1/4 = 25%

But, if something went from 10 to 8, the percent decrease is just

(10 - 8) / 10 = 2/10 = 20%

You start off with 100% of the total

If it is Decreased by 5%  it goes Down by 5%  so you end up with  (100-5)% = 95%

You can either find 5% and take it off the original amount OR you can just find 95% to start with

If it is Increased by 5%  it goes up by 5%  so you end up with  (100+5)% = 105%

You can either find 5% and add it to the original amount OR you can just find 105% to start with.

So just remember D is for Decrease and for Down