What is a part to whole ratio?

A part to whole ratio compares the part of something to the whole of that same thing. It is usually expressed as a fraction, with the part being the numerator and the whole being the denominator. For example, if a pizza is divided into 8 equal slices and someone eats 3 slices, the part to whole ratio of the slices eaten to the total slices would be 3/8. Part to whole ratios are commonly used in mathematics, finance, and statistics to compare proportions and percentages.