Percentages explained with step-by-step examples, the GST one-eleventh rule, footy stats and mental maths tricks for Aussie kids.
Next time you're at the checkout, look at the total on your receipt. Somewhere inside that number is GST, Australia's 10% goods and services tax, quietly baked into almost everything you buy. That's percentages in action before your child has even opened a textbook.
Percentages explained simply come down to one idea: comparing a number to 100. Once that clicks, most of the confusion disappears. This guide covers what is a percentage, how percentages work step by step, and enough real Aussie examples, GST included, that your child can actually apply it.
A percentage is a way of expressing a number as a fraction of 100. When you see 50%, it means 50 out of every 100, exactly the same amount as the fraction 1/2 or the decimal 0.5. Percentages are just a standardised way of comparing amounts, so 75% always means "three-quarters of the whole," no matter what the whole actually is.
"Percent" comes from the Latin per centum, meaning "per hundred." That's the whole idea in two words: a percentage always tells you how many parts out of a hundred you're talking about. Once a child understands that "%" simply means "out of 100," the symbol stops being mysterious.
At its core, calculating a percentage of a number uses one formula:
Percentage of a number = (Percentage ÷ 100) × Number
For example, to find 20% of 50:
(20 ÷ 100) × 50 = 0.2 × 50 = 10
Every percentage calculation, however it's dressed up, comes back to this same relationship.
Here's a genuinely useful, Australia-specific percentage trick. Because GST is a flat 10% nationwide (unlike some countries where sales tax varies by region), the tax hidden inside a GST-inclusive price is always exactly one-eleventh of the total.
Here's why: 10 parts of the pre-tax price plus 1 part of tax makes 11 equal parts in the final total, so the tax is always 1 of those 11 parts.
Worked example: A meal costs $66 including GST. How much of that is tax?
$66 ÷ 11 = $6 in GST, meaning the meal itself cost $60 before tax.
This is a great real example to practise with, since it's a genuine mental-math shortcut real Australian adults use, not just a textbook exercise.
Percentages, decimals, and fractions are three ways of writing the same value. Being able to move between them is one of the most useful maths skills a child builds in primary school.
To turn a percentage into a decimal, divide by 100 (move the decimal point two places left). To turn a decimal into a percentage, do the reverse. Our companion guide on what is a fraction covers the fraction side of this same relationship in more depth.
Worked example: A student scores 42 out of 50 on a test. What percentage is that?
(42 ÷ 50) × 100 = 84%
Percentages aren't just about finding a portion of something, they're also used to describe how much something has gone up or down.
Percentage increase: New amount is larger than the original. (Increase ÷ Original) × 100
Percentage decrease: New amount is smaller than the original, most commonly seen in sale discounts. (Decrease ÷ Original) × 100
Worked example: A $40 jumper is on sale for $30. What's the percentage decrease?
($10 decrease ÷ $40 original) × 100 = 25% off
Sport is one of the easiest, most genuinely engaging ways to make percentages click for Aussie kids:
A few shortcuts make percentages faster without a calculator:
Percentages typically enter the curriculum once students already have a working understanding of fractions, since the two concepts are taught as connected ideas. Under the Australian Curriculum, percentages are introduced around Year 5, at the same point the increased focus on fraction equivalence deepens, building toward more complex percentage problems (increase, decrease, and real-world applications) through Year 6 and beyond.
Curriculum pacing can vary somewhat by school and state, but this general progression holds broadly across Australia.
Percentages keep showing up well past school maths. Savings accounts and loans both use interest rates expressed as percentages, and even HECS-HELP student loans are indexed each year by a percentage rate, meaning the same core skill (converting a rate to a decimal and multiplying) applies just as much to adult finances as it does to a Year 5 worksheet.
Simple interest example: $500 saved at a 4% annual interest rate for 1 year earns:
500 × 0.04 × 1 = $20
This is genuinely one of the more useful "why does this even matter" moments for older students, since it connects classroom percentages directly to money decisions they'll actually make.
A few low-effort habits build percentage fluency without turning it into extra homework:
Try these with your child to check understanding:
Maths educators generally recommend teaching percentages only after fractions are reasonably solid, since a percentage is essentially a specific, standardised way of writing a fraction (always out of 100) rather than a separate topic. This matches the sequencing used under the Australian Curriculum, where percentages are introduced alongside the deepening focus on fraction equivalence in Year 5, rather than as an unrelated new topic.
Percentages sit at the intersection of fractions, decimals, and real-world maths, which means a shaky foundation in any one of the three can make percentages feel harder than they actually are. TutorExel tutors work through percentages using the same step-by-step formula and real-life examples covered here, adjusted to whichever piece your child's specific gap is in. You can see how maths support is organised by year level on the subject pages.
What is a percentage in simple terms?
A percentage is a way of expressing a number as a portion of 100. Fifty percent (50%) means 50 out of every 100, the same amount as the fraction 1/2 or the decimal 0.5.
How do percentages work when calculating a discount?
A discount percentage tells you how much is being taken off, not what you'll pay. "30% off" means you pay 70% of the original price, calculated as the original price minus 30% of that price.
What year do kids in Australia learn percentages?
Percentages are typically formally introduced around Year 5, once students already have a working understanding of fractions, with more advanced percentage problems building through Year 6 and beyond.
How do you work out GST from a total price?
Since Australia's GST is a flat 10%, divide the GST-inclusive total by 11 to find the tax component. For example, $110 ÷ 11 = $10 in GST.
Why do students find percentages confusing?
The most common source of confusion is skipping the step of converting a percentage to a decimal before calculating, or misunderstanding what a percentage increase or decrease is actually being calculated against.
Is there a quick way to calculate percentages without a calculator?
Yes. Finding 10% (move the decimal one place) and adjusting from there covers most everyday percentage calculations, including sale discounts and quick estimates.
If percentages still feel shaky at home, a bit of structured practice connecting them back to fractions usually closes the gap fast. Book a free assessment with TutorExel to get a maths plan built around exactly where your child needs it.
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