Feeling hungry? Have a slice of pie ;)

Pie charts

Pie charts….. Let us see a set of data very easily Without using numbers Here’s one now……

Every pie chart has… A title A key Sectors These follow….

Title

A key

Sectors

More pie charts

Now let’s try a real one Do a survey of the group and whether people prefer tea, coffee or neither, using the tally method Let’s see what that looks like as a pie chart End E3 here

Constructing a chart Doing the Maths bit…

Back to the Babylonians They divided a circle into 360 degrees This matched the number of days in a year very closely It is also a number with many factors, so it is easy to divide down and calculate with, without getting into fractions ;)

Check out the factors of 360 On your own or in pairs, work out as many factors of 360 as you can Answers follow…

Factors of

Factors of

Factors of

Working out the angles… Let’s imagine we do a survey of 12 people to find out whether they prefer tea, coffee, or some other drink Let’s say there is 1 who prefers tea, 8 coffee and 3 some other drink…

Working it out…. Then 1 in 12 prefer tea 8 out of 12 prefer coffee 3 out of 12 prefer “other” drinks

Changing the English to Maths 1 in 12 for tea = 1/12 8 out of 12 for coffee = 8/12 3 out of 12 for “other” = 3/12

Calculating the angles 1 tea out of 12 8 coffee out of 12 3 “other” out of 12 Tea sector = 1/12 x 360 Coffee = 8/12 x 360 “Other” = 3/12 x 360

Do the Maths….for tea 1 x You can put any number over 1 - this doesn’t change its value, and lets you multiply it as a fraction 1 x

Sector size for tea 1 x x 360 = divided by 12 = 30 So the sector for tea will be 30 degrees wide

Do the Maths….for coffee 8 x You can put any number over 1 - this doesn’t change its value, and lets you multiply it as a fraction 8 x

Sector size for coffee 8 x x Reduce 8/12 to its lowest terms – 2/3 Either do 360 x 2 and divide by 3 Or divide the 360 first by 3 then double it = 240 degrees

Boxing clever Some people always work out the basic sector first and then multiply up from that We know 1/12 prefer tea = 30 degrees Coffee is 8/12 – so that will be 8 x 30! Now let’s see the “other” category

Sector size for “other” 3/12 prefer “other” We know 1/12 = 30 degrees So 3/12 will be 90 degrees (90°) Also, 3/12 = ¼, and a quarter of a circle is 90°

Looks like this…