Money Calculations

What currencies can be used?

Many different currencies are used
The most commonly used currencies are
- US Dollars ($ or USD)
- Great British Pounds (£ or GBP)
- Euros (€ or Euros)
- It is possible to see other currencies used, with or without their symbols

What might I be asked to do in money calculations?

Read exam questions carefully to identify key words
- Total or sum will mean to add up
- Difference or increase/decrease in costs will involve subtracting
- Changing from one currency to another (exchange rates) will involve multiplying or dividing
Some questions may involve a combination of these
- E.g., Working out the total cost of an energy bill
Questions that involve money may also involve other topics in the course
- E.g., Fractions, percentages, simple and compound interest etc.

How should I round values in a money calculation?

Many currencies will be rounded to two decimal places
- Dollars, pounds and euro should all be used to two decimal places
- Always write down both decimal places, even if the second is zero
  - This is particularly important when using a calculator
  - 1.4 dollars on a calculator should be written as $1.40
For a question involving large numbers such as the cost of a car
- Rounding to the nearest dollar, 10 dollars or 100 dollars may be more appropriate
  - Use the information in the question to make a judgement
Some currencies have large numbers due to exchange rates
- These are usually rounded to the nearest whole number
- E.g., $10 is 816.38 rupees making $100 the same as 8163.80 rupees
  - Rounding the exchange rate to $100 is 8160 rupees would be appropriate

What should I do when money calculations involve more than two decimal places?

In some contexts money facts may be given to more than two decimal places
- E.g. One litre of petrol in the UK costs an average price of £1.579
Use all of the decimal places given in your working
- Round (to two decimal places or whatever is appropriate) for your final answer only

Exam Tip

Use the information given in the question to decide how to round your final answer
Check that your answer matches the currency in the question

Worked example

In his favourite UK fashion store, Thomas buys 4 t-shirts costing £8.50 each and 2 pairs of shorts costing £7.20 each. On his way home Thomas fills his car up with 45 litres of petrol at a price of £1.579 per litre.

Find out how much Thomas spent in total on clothes and petrol.

Find the total cost of the t-shirts, shorts and petrol separately
Use the figures as they are given, do not round any at this stage

$4 \times 8.50 = 34 2 \times 7.20 = 14.4 45 \times 1.579 = 71.055$

Total (add) these amounts

$34 + 14.4 + 71.055 = 119.455$

The currency is Great British Pounds (£) and values are relatively small so it makes sense to round the final answer to two decimal places

Thomas spends a total of £119.46 on clothes and petrol

Money Calculations (CIE IGCSE Maths: Core)

Revision Note