How to Find the Percentage Increase or Decrease of a Number


Hi, my name is Marija, and today I'm gonna show you how to find the percentage increase or decrease of a number, and the formula is the same for both. So, the way that we're gonna find the percent of, we'll call it change, since we don't know if it's increase or decrease, is you're going to take the new value, subtract it from the old value, and then you're gonna divide by the old value. And, once you get this number, you're gonna multiply it by 100 in order to make it into a percent. So, let's say, for example, that a price has changed from five dollars to 10 dollars, and you wanna know what the percent increase is. We're gonna take the new value, which is 10 dollars, minus the old value, which was five dollars, and then we're gonna divide that by the old value, which was five dollars. So, we have 10 minus five is five, over five, and we get one, and now, we have to divide this number by 100 in order to turn it into a percent, so we do one times 100. And, we find out the percent of increase was 100 percent, and we know it was an increase because the number that we got was positive and also, because the new value was larger than the old value, so obviously, it increased. So, there was a 100 percent increase from five to 10. So, to find the percent of change, whether it's increase or decrease, you do the new value minus the old value, divide that by the old, and then multiply it by 100 to make it a percent.

Marija Kero graduated from the Pforzheimer Honors College at Pace University with a Bachelor's Degree in Mathematics and Adolescent Education.