Scientific American presents Math Dude by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies. Long time math fans may remember our first foray into the world ...

Calculate annual % change by dividing start by end value, raising to inverse years, minus one, times 100. Ex: a drop from $15M to $10M over 2 years is a 18.4% average annual decline. This calculation ...

How to calculate percentages is easier than you think. Quick, what’s 36% of 25? Or how about 250% of 20? Learn a quick and dirty tip to help you calculate all of those pesky percentages in your head.