Cambridge International Mathematics

Graphs, charts and tables (Chapter 5) 113

PIE CHART

Apie chartpresents data in a circle. The circle is divided into

sectors which represent the categories. The size of each sector is

proportional to the quantity it represents, so its sector angle can be

found as a fraction of 360 o.

Example 2 Self Tutor

For the data on teachers’ mode of transport inExample 1:

a calculate the sector angles b construct a pie chart.

a For car,^1530 £ 360 o= 180o

For bicycle, 303 £ 360 o=36o

For bus, 307 £ 360 o=84o

For walk, 305 £ 360 o=60o.

b Mode of transport to school

SCATTER DIAGRAMS AND LINE GRAPH

We are often given data which shows how one quantityvarieswith another. The data will be given as ordered

pairs which we can plot on a set of axes.

If the data isdiscrete, it does not make sense to join the points and we have ascatter diagram.

For example, if each apple at a market stall costs 20 pence, we

obtain a scatter diagram. It does not make sense to buy a part of

an apple.

If the data iscontinuouswe can join the points with straight lines to

form aline graph. We often obtain line graphs when we observe

a quantity that varies with time. You will see this in the following

example:

Example 3 Self Tutor

The temperature at Geneva airport was measured each hour and the results recorded in the table below.

Draw a line graph to illustrate this data.

Time 080009001000110012001300140015001600170018001900

Temperature(oC) 5 8 11 12 15 16 18 14 12 11 11 9

Pie chart

Car

Bicycle

Bus

Walk

180°

60° 36°

84°

0

20

40

60

80

100

012345

cost (pence)

number of apples

IGCSE01

cyan magenta yellow black

(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_05\113IGCSE01_05.CDR Thursday, 18 September 2008 11:48:25 AM PETER