© Nuffield Foundation 2011

Nuffield Mathematics Activity

Currency conversion

© Nuffield Foundation 2011

Would you like to go abroad for a holiday?

If you change some spending money from pounds to another currency, how much will you get?

This activity shows some ways to work out this and other conversions.

© Nuffield Foundation 2011

Suppose £1 = $1.50.

A graph can be used to convert pounds to dollars.

What is the scale on each axis?

Why must the graph go through (0, 0)?How could you use the graph to find out what $8 is in £s?

Would you prefer to use the graph or a conversion factor to change between dollars and pounds?

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Dolla

rs ($

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Pounds (£)

Conversion graph for pounds (£) and US dollars ($)

© Nuffield Foundation 2011

The graph is a straight line through (0, 0). This means that the number of dollars is directly proportional to the number of pounds. Each extra £ 1 gives an extra $1.50

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Dolla

rs ($

)

Pounds (£)

Conversion graph for pounds (£) and US dollars ($)

© Nuffield Foundation 2011

From the gradient: the number of dollars = 1.5 the number of £s.

1.5 is the conversion factor for this graph.

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0 1 2 3 4 5 6 7 8 9 10

Dolla

rs ($

)

Pounds (£)

Conversion graph for pounds (£) and US dollars ($)

Gradient = 15/10 = 1.5

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© Nuffield Foundation 2011

Currency conversionAt the end of the activity

Have you ever used line graphs in other situations such as science experiments, to find a relationship?

Do you prefer to use a graph or a conversion factor to convert quantities from one unit to another?

In direct proportion, doubling one quantity doubles the other. Does the same rule work if you multiply by 3 or by 5?