If you decrease something by 4 percent,
you are keeping (100% - 4%) or 96% of the original
so multiply by the original amount by 96 percent or .96
If you have 100 pennies, and you give 4 away ( 4 percent decrease), you still have 96 pennies. You are keeping 96 percent of what you started with. This works no matter how much you start with.
Example:
you have 40 dollars
4% decrease
40 * .04 = 1.6 take this away
40 - 1.6 = 38.4 left
you keep 96 percent
40 * .96 = 38.4 left
