Variation and power

modelling

30

Contents:

A Direct variation [2.13]

B Inverse variation [2.13]

C Variation modelling [2.13]

D Power modelling

Opening problem

#endboxedheading

A shop sells cans of soft drink forE 2. Suppose we buyncans and the total cost isEC.

To study the relationship between the two variablesnumber of cansandtotal cost, we can use a table

of values or a graph.

n 0 1 2 3 4 5

C 0 2 4 6 8 10

The graph ofCagainstnconsists of discrete

points because we can only buy a whole

number of cans. However, an imagined line

passing through these points would also pass

through the origin.

Things to think about:

² Which of the following are true:

I doubling the number of cans doubles the total cost

I halving the number of cans halves the total cost

I increasing the number of cans by30%increases the cost by30%?

² How can we describe the relationship betweennandC?

2

4

6

8

10

12345

C()E

n(cans)

O

[2.13, 11.2]

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Y:\HAESE\IGCSE01\IG01_30\605IGCSE01_30.CDR Tuesday, 18 November 2008 12:00:56 PM PETER