PIE CHARTS PIE CHARTS

Calculating angles and percentagesCalculating angles and percentages

Materials needed• Classwork book (to copy notes)• Protractor• Pair of compasses• Pencil• Ruler• Eraser

Lesson Objective• To be able to draw a pie chart by

calculating the degrees for each sector from a set of given data

• To be able to calculate the percentage for each sector from a set of given data

Why Pie charts?• A pie chart is a good way of displaying

data when you want to show how something is shared or divided.

How do we calculate angles?

• Twenty students were asked on which day they would paint the scenery for the school play. The replies were:

• Monday - 5• Tuesday - 4• Wednesday - 8• Thursday 3

Remember!!!• The angles at the centre of a pie chart

MUST add up to 360º

Calculation• 20 students are represented by 360º• One student is represented by 360º = 18º 20Monday = 5 x 18º = 90º

Tuesday = 4 x 18º = 72º

Wednesday = 8 x 18º = 144º

Thursday = 3 x 18º = 54º

Now….• Draw the pie chart representing the

students

• Show the key and angle of each sector.

• Then, calculate the percentage of each parts.

Peer Assessment• Ask your friends to check your workings:

– Circle (1 point)– Correct angles and sector (4 points)– Key shown for days (1 point)– Percentage shown (4 points)

• Total up the number of points (max=10)• 8 - 10 points = 3 stars• 5 - 7 points = 2 stars• 2 - 4 points = 1 star

Well Done!!!• How well did you do in this exercise?

• How many stars did you get?

• Anyone got 3 stars?