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Teaching mathematics
Teaching mathematics

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Exchange rates

A common use for proportionality is currency exchange rates. When you change your money at the Post Office or travel agent ‘commission free’, they will use a different exchange rate when they sell you foreign currency to when they buy it, thus making a profit.

Activity 10 Example problem: Japanese yen

Timing: Allow 5 minutes

Zoë is going on holiday from England to Japan.

Before leaving, she changes 1500 pounds sterling (GBP) into Japanese yen (JPY).

The exchange rate is 1 GBP = 177.415 JPY.

Calculate the amount of foreign currency Zoë takes on holiday.


This question is quite straightforward since you are given the unit rate for £1 in yen. All that is required here is to multiply the number of pounds by the rate, giving 266 122.50 yen.

If the rate was given in another form, for instance: 20 GBP = 3548.30 JPY, another step would be needed to calculate the unit rate.