HDY calculate percentage of increase that involves a negative number on one side of the equation?
That depends on what you're asking.
If you mean something like "what's the increase if you have 110% of -20," that's an awkward way of saying it because there isn't really an increase.
110% of -20 = 1.1 * -20 = -22
That's an increase, sort of, of -2 from -20, but since it's -2 it's not really an increase.
A better way to word it would be "what is the change if you have 110% of -20?"
Then the change is -2, but you're not confusing things by trying to call -2 an "increase."
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(570,000) to 640,000= what percent of increase?
640000 - 570000 = 70000
70000/570000 = about 0.1228 = about 12.28%