How to work out a percentage

Percent of a number. Divide the percent by 100, then multiply by the number. So 15 percent of 200 is 0.15 times 200, which is 30.

What percent one number is of another. Divide the first number by the second, then multiply by 100. So 30 out of 200 is 0.15 times 100, which is 15 percent.

Percent change. Subtract the old value from the new value, divide by the old value, then multiply by 100. Going from 200 to 250 is 50 divided by 200 times 100, which is a 25 percent increase.