Lesson 2, Topic 3
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# Pie Chart

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Pie charts help show proportions and percentages between categories, by dividing a circle into proportional segments. Each arc length represents a proportion of each category while the full circle represents the total sum of all the data, equal to 100%.

Pie charts are ideal for giving the reader a quick idea of the proportional distribution of the data.

### Example

Draw a Pie chart with the given angles 50º, 70º, 140º, 100º

Solution:

Recall that the sum of angles in a circle equal 360º, so these angles must add up to 360º.

i.e.  50º +  70º  +   140º +  100º  =   360º

First Step: Draw a circle with centre O. Then draw radius OA.

Second Step: Place your protractor to draw each angle and label the diagrams as shown above.

Place your protractor along OA and measure angle AOB   =   50º.

Third Step: Place your protractor along OB and measure angle BOC   =  70º

Fourth Step: Place your protractor along OC and measure angle COD   =  140º

Fifth Step: Verify that angle ODA  =   100º

### Find the angles of a Pie Chart:

Example:

Segun was given N600 in July as pocket money. He spent the money as follows:

Draw a pie chart to illustrate the data.

Solution:

There are 360º in a full circle and the total amount spent was N600 is represented by 360º.

∴  Express each value as a fraction of the total.

By multiplying the fraction by 360º

i.e Food angle for N200    =    $$\frac{200}{600} \scriptsize \: \times \: 360^o \\ \scriptsize = 120^o$$