Thinking Skills: Critical Thinking and Problem Solving

3.7 Recognising patterns 103

Commentary
This question is actually quite easy. It is only a
matter of being careful and matching
appliance to bar length correctly. The main
complication (and this is a potential trap for
those who don’t look at the question and the
graphs carefully) is that the order of the
appliances in the graphs is different in some
cases from the order in the table. Also, the
exact heights of the bars cannot always be read
accurately enough at the scale on which the
graphs are drawn, so it is necessary to look at
the relative heights of the different bars.
In fact D is the correct graph. The appliances
have been put into order by their percentage
ownership. A has the appliances ordered as for
D but the bars are in the order of the table. The
other graphs have similar errors – you might
like to identify the error in each case.

Commentary

The data expressed in local currency is not very

useful for a direct comparison. It is easier if the

costs are all expressed as percentages so that

the appropriate components can be compared.

The table is repeated below with the costs as

percentages of the totals for each country.

Sudaria Idani Anguda Boralia

Crude oil 51.09 36.00 30.10 47.62

Refining 1.46 9.00 1.50 1.90

Wholesale 6.57 7.00 3.76 13.33

Retail 4.38 4.00 4.36 4.76

Tax 36.50 44.00 60.27 32.38

In the pie chart, the largest segment is just

under half the area. It could, therefore, only be

tax in Idani or crude oil in Boralia. We cannot

easily distinguish which as the difference in

the second-largest segments is not very great.

We must, therefore, look at the smallest three

segments. Boralia has one (wholesale) three

times the size of either of the other two, but in

the pie chart they are much closer than this,

so the answer must be Idani.

This activity reverses the skill shown above:

the graph is given (a pie chart in this case)

and the cost structure it represents has to be

identified.

A student is drawing pie charts to show

how the various elements of the cost of fuel

contribute to the total price in various

countries. The data she is using is shown

below, with the prices in local currencies.

Sudaria Idani Anguda Boralia

Crude oil 0.70 18.68 0.40 0.50

Refining 0.02 4.67 0.02 0.02

Wholesale 0.09 3.63 0.05 0.14

Retail 0.06 2.08 0.06 0.05

Tax 0.50 22.84 0.80 0.34

Total 1.37 51.90 1.33 1.05

Activity

She drew one pie chart last night, but has

not labelled the segments and cannot

remember which country it represents. The

pie chart is shown below.

Which country is it?