Money Calculations
What currencies can be 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
- Rounding to the nearest dollar, 10 dollars or 100 dollars may be more appropriate
- 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
Examiner 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
Total (add) these amounts
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