12/45 expressed as a percentage is 26.67%. This rounded figure tells you that the fraction is just over a quarter of a whole.
The fraction 12/45 can be simplified to 4/15, which still represents the same part of a whole. Whether you use the fraction or the percentage, the value stays the same.
Knowing both forms is useful: fractions work well in exact calculations, while percentages are handy for quick comparisons, like seeing that 26.67% of a class of 45 students would be about 12 students.
