How to solve percent of increase and decrease math problems? I'm Bon Crowder with MathFour.com, and we're talking about how to find the increase or decrease in percent for any given problem. Here we have a problem, Bon's lipstick was eleven dollars. Now, it went up to 15 dollars. What is the percent of increase? The way we do this, is we find the absolute value of the difference in the two numbers, and divide it by the original value. So, what we have is, it was 11 dollars, now it's 15. So, we do that difference, which is a subtraction problem and divide it by the original number, which is 11. 11 minus 15 is negative four and the absolute value of negative four is four. So, that's four over 11. And then, we convert that to percentage, which means we divide 11 into four. And that gives us 36 percent increase. Now, what happens if the lipstick goes down in price? So, start at 11, 36 percent increase to 15 and now, its going to go down to 12 dollars. What's the percent decrease? We can use the same formula, absolute value of the difference. So, 15 minus 12, divided by the original value. And now the original value is 15. So, 15 minus 12 is three, the absolute value of three is still three. And three over 15 is one-fifth or 20 percent. So, we have a 20 percent decrease. And that's how you solve percent increase and percent decrease problems. I'm Bon Crowder with MathFour.com, have fun with it.