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Cambridge (CIE) IGCSE Maths

Revision Notes
(Time, Currency & Unit Conversions)

Exchange Rates

Exchange Rates

Understanding Exchange Rates

An exchange rate is the value of one currency expressed in terms of another currency. It tells you how much of one currency you can get with a unit of another currency.

Currencies are always quoted in pairs, for example, GBP/USD or EUR/GBP. The first currency in the pair is called the base currency, and the second is the quote currency. The exchange rate shows how much of the quote currency you get for one unit of the base currency.

For example, if the exchange rate for GBP/USD is 1.30, it means £1\text{£}1 (one British pound) can be exchanged for $1.30\$1.30 (one dollar and thirty cents).

There are two common types of exchange rates you might see:

  • Buying rate: The rate at which a bank or exchange service will buy foreign currency from you.
  • Selling rate: The rate at which a bank or exchange service will sell foreign currency to you.

The selling rate is usually higher than the buying rate, allowing the bank to make a profit on the exchange.

  • Remember, exchange rates fluctuate constantly due to market demand and supply.
  • The base currency is always 1 unit; the exchange rate tells you how many units of the quote currency you get.

Converting Currency

To convert between currencies, you use the exchange rate as a multiplier or divisor depending on the direction of conversion.

Converting from foreign currency to home currency (e.g. from USD to GBP):

Divide the amount in foreign currency by the exchange rate (if the rate is given as home currency per foreign currency unit), or multiply by the inverse rate.

Converting from home currency to foreign currency (e.g. from GBP to USD):

Multiply the amount in home currency by the exchange rate (if the rate is given as foreign currency per home currency unit).

It is important to check whether the exchange rate is quoted as the amount of foreign currency per unit of home currency or vice versa. Usually, the rate is given as how many units of foreign currency equal one unit of home currency.

For instance, if the exchange rate is £1=$1.30\text{£}1 = \$1.30, then:

  • To convert £50\text{£}50 to dollars: 50×1.30=65$50 \times 1.30 = 65\,\mathrm{\$}
  • To convert $65\$65 to pounds: 651.30=50£\frac{65}{1.30} = 50\,\mathrm{\text{£}}

Always be clear about which currency you start with and which you want to convert to.

For example, if you have 100\text{€}100 and the exchange rate is £1=1.15\text{£}1 = \text{€}1.15, to find how many pounds you get:

Pounds=1001.1586.96£\text{Pounds} = \frac{100}{1.15} \approx 86.96\,\mathrm{\text{£}}

  • Check the direction of the exchange rate before converting.
  • Use division when converting from foreign to home currency if the rate is given as home currency per foreign currency.
  • Use multiplication when converting from home to foreign currency if the rate is given as foreign currency per home currency.

For instance, if the exchange rate is £1=$1.30\text{£}1 = \$1.30, converting £100\text{£}100 to dollars is:

Dollars=100×1.30=130$\text{Dollars} = 100 \times 1.30 = 130\,\mathrm{\$}

Practical Applications

Exchange rates are used in many real-life situations such as travelling abroad, buying goods online from other countries, or businesses trading internationally.

When calculating the cost of an item in a different currency, you multiply or divide by the exchange rate depending on the direction of conversion.

Changes in exchange rates affect how much you pay or receive. For example, if the pound strengthens against the dollar (the exchange rate increases), British travellers will get more dollars for their pounds, making travel cheaper in the USA.

Conversely, if the pound weakens, the same amount of pounds buys fewer dollars, making travel or imports more expensive.

Businesses must keep an eye on exchange rates to manage costs and pricing when dealing with foreign currencies.

For example, if a UK company imports goods costing $500\$500 and the exchange rate is £1=$1.25\text{£}1 = \$1.25, the cost in pounds is:

5001.25=400£\frac{500}{1.25} = 400\,\mathrm{\text{£}}

If the exchange rate changes to £1=$1.20\text{£}1 = \$1.20, the cost becomes:

5001.20416.67£\frac{500}{1.20} \approx 416.67\,\mathrm{\text{£}}

The company now pays more pounds for the same goods due to the weaker pound.

  • When exchange rates change, the cost in your home currency changes inversely.
  • Stronger home currency means foreign goods are cheaper; weaker home currency means they are more expensive.

Example: If you are travelling to France and the exchange rate is £1=1.15\text{£}1 = \text{€}1.15, and you want to exchange £200\text{£}200 into euros:

Euros=200×1.15=230\text{Euros} = 200 \times 1.15 = 230\,\mathrm{\text{€}}

PracticeExample 8

Worked Example

Example: Convert 150\text{€}150 to pounds if the exchange rate is £1=1.20\text{£}1 = \text{€}1.20.

PracticeExample 9

Worked Example

Example: A US product costs $250\$250. If the exchange rate is £1=$1.40\text{£}1 = \$1.40, how much does it cost in pounds?

PracticeExample 10

Worked Example

Example: You have £300\text{£}300 and want to buy Japanese yen. The exchange rate is £1=¥150\text{£}1 = \text{¥}150. How many yen will you get?

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