Percentages are often written with a percent sign.
e.g. the number 0.55 can be expressed as "55%" read "fifty-five percent". An alternative, e.g. saying "fifty-five hundredths" is less preferred, not least because it's homophonous with "fifty five-hundredths", which is 50/500 = 0.1
Fractions are often expressed as percentages, even when the fraction could be simplified.
Test scores are often expressed as percentages.