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# How to explain pie charts

Updated April 17, 2017

Pie charts provide a graphical representation of data. Data percentages in a pie chart always add up to 100% so that the pie chart provides a summary of all responses to a question or answers to a problem. Students in elementary school usually learn about pie charts in the fourth through sixth grades. At this age, the critical concepts needed to understand pie charts include percentages, degrees and fractions. An explanation of pie charts helps in understanding this basic method of displaying data.

Draw a basic pie chart on a chalkboard or white board. Divide the pie chart into two halves. Tell the group that pie charts represent data using percentages that add up to 100 per cent, or one whole pie. Ask if they can recognise the percentage of a slice taking up one-half of the pie.

Draw another example of a pie chart, this time dividing the one half of the pie into halves again, creating a chart with one half piece and two quarter pieces. Ask the group if they can recognise the percentages of all three sections and whether they add up to 100 per cent.

Label each section of the pie chart with its percentage and explain that for a pie chart to be useful it must contain the data's percentages. Remind the group that they should set pieces in a pie chart in increasing order of size going in a clockwise direction.

Ask the group or an individual to come up with a group of percentages that equal 100 per cent and to draw a corresponding pie chart. Offer a list of common data sets and the equivalent percentages, such as a pie chart with three equal sections of 33.33 per cent each.

Explain the link between the percentage of a piece in the pie chart and the degree of the angle for that piece. A circle has 360 degrees, making 1 per cent of a circle take up 3.6 degrees. You can multiply 3.6 degrees by the percentage of a section to get the degree of the angle for that section.