a. how much the different parts of something contribute to the whole
Pie charts are useful for representing how much the different parts of something contribute to the whole. It presents data in an easy-to-read pie slice format which would tell the reader how much of one data element exists. When a certain element takes a bigger part in the pie chart meaning that element has a higher statistics or data compared to other elements. Comparison is one of the main reasons for pie charts. In pie chart you can compare what element is bigger than the others or what is smaller compared to the rest of the elements.
