Twenty percent of 30 is 6. "Percent" means "per 100," or "divided by 100," so calculating 20 percent entails multiplying by 20 and dividing by 100, which is the same as multiplying by 0.20.
Written out, the formula for calculating 20 percent of 30 is 30 x (20 / 100) = 6. Alternatively, this amount could be expressed as two-tenths of 30, one-fifth of 30 or 0.2 of 30.
Percentages are a popular way to express fractions because the numbers between zero and 100 are familiar to most people and are easy to say and write. One-hundred is also a straightforward common denominator to use, while fractions that use other denominators can be more complicated to inter-convert and more difficult to understand quickly.