What is the purpose of a pie chart and when do you use one?

Math and science. You use a pie chart to compare how much you have of something ... I think

A pie chart can be used for visualizing data and you can use one for percentage results such as; your classmates like blue and some like green and some like purple, you could use a pie chart to find the percent of classmates that like each color by collecting data by asking what their favorite color is. Then you can put the data into the pie chart to see how many people like a certain color.