consumer maths


  • Interest is a lender’s reward for providing funds to a borrower.
  • In finance, a lender typically expects a larger rate of interest for longer loan terms.
  • One method of interest calculation is simple interest. This is where interest is calculated on the original principal – the formula being I = PRT.
  • Another method is compound interest where interest is calculated on the changing principal – the formula being I = P x [1+R]t – P.


  • Goods and services sometimes have discounts at certain times of the year.
  • This video outlines the methods to calculate the discount when the reduced price is missing, and the discount applied when the original price is missing.

currencies & conversions

  • When traveling overseas or making international online transactions, knowing how to convert currencies becomes very useful.
  • Currency exchanges assign each currency a three-letter symbol. For example, the Australian dollar is AUD.
  • Currency pairs show the exchange rate from one currency into another. For example, the exchange rate from Australian dollars into euros is presented as AUD/EUR.
  • When performing conversions it is necessary to identify the base currency (on the left) and the quote currency (on the right).

penalty rates & commissions

  • Employers sometimes provide additional payments during inconvenient working periods, or for high performance in certain roles.
  • This video outlines how to calculate total pay when penalty rates and commissions apply.


  • Employers must present employees with a payslip within 1 day of pay.
  • This document needs to specify details such as work period, leave entitlements, gross pay, and tax deducted.
  • Unless arranged beforehand, employers deduct pay from employees in the form of PAYG (pay-as-you-go) tax payments to the ATO. These details are important to keep come financial year end when completing a tax return.
  • Employers contribute superannuation to a fund which you have chosen, and this money is on top of gross pay. As of 2017/18 financial year, this payment is 9.5% of gross pay.


The Goods and services tax (or GST) is a broad-based tax that applies to most goods and services in Australia. It was introduced by the Howard government in 2000. If a business has revenues above a certain threshold, it is compulsory that it collects GST on behalf of the government. Ultimately it is the consumer who bears the additional cost. GST is currently 10%.


Problem 1: If the original price of a book is $50, what is the retail price after GST has been applied?

Answer: Multiply $50 by 1.10. The answer is $55.


Problem 2: If the retail price of a chair is $88, what is the original price before GST was applied?

Answer: Divide $88 by 11, and then multiply by 10. The answer is $80.

take consumer maths quiz

Free Divi WordPress Theme, Find new Free Android Games at