# Feeling hungry? - PowerPoint PPT Presentation

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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.

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Feeling hungry?

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## 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

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…

1

2

3

4

5

6

8

• 9

• 10

• 12

• 15

• 18

• 20

• 30

• 36

• 40

• 45

• 60

• 72

• 90

• 120

• 180

### 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

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 360

12

You can put any number over 1 - this doesn’t change its value, and lets you multiply it as a fraction

• 1 x 360

12 1

1 x 360

12 1

1 x 360 = 360

360 divided by 12 = 30

So the sector for tea will be 30 degrees wide

### Sector size for tea

Do the Maths….for coffee

• 8 x 360

12

You can put any number over 1 - this doesn’t change its value, and lets you multiply it as a fraction

• 8 x 360

12 1

Sector size for coffee

• 8 x 360

12 1

• 2 x 360

3 1

• 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°