Common Maths Mistakes High School Students
Your child spends an hour studying Maths, understands the examples in class and finishes their homework. Then the test results arrive, and the marks don't match the effort.
Sound familiar?
For many high school students, the difficulty isn't always understanding an entire topic. Sometimes, small mistakes with calculations, algebra or problem-solving lead to incorrect answers.
The good news is that many of these errors can be identified and worked on with the right practice.
Five Maths mistakes worth watching for are incorrect order of operations, confusion with negative numbers, fraction errors, algebra mistakes and misinterpreting word problems.
If your child is in Year 7, 8, 9 or 10, here are five common mistakes to look out for and practical ways to help them.
1. Getting the Order of Operations Wrong
One common mistake is solving calculations from left to right without considering the correct order of operations.
Take this example:
6 + 2 × 3 = ?
A student might add 6 + 2 first and then multiply the result by 3, getting 24.
But the correct answer is 12.
Correct working:
6 + (2 × 3) = 6 + 6 = 12
In Australian schools, students often learn the order of operations using BODMAS.
This stands for:
- Brackets
- Orders
- Division and Multiplication
- Addition and Subtraction
Multiplication and division have equal priority and are completed from left to right. The same applies to addition and subtraction.
How to Fix It
Encourage your child to identify which operation should be completed first before starting the calculation.
Practise a few questions that look similar but have different answers because of brackets.
For example:
- 5 + 3 × 2 = 11
- (5 + 3) × 2 = 16
Ask your child to explain why the answers are different.
Understanding the rule is more useful than simply memorising the answer.
2. Making Mistakes with Negative Numbers
Negative numbers can become confusing when students begin working with more complicated calculations and algebra.
For example:
-3 + 8 = ?
The correct answer is 5.
However, some students treat the negative sign incorrectly and end up with the wrong result.
Another example is:
-3 - 8 = -11
These two calculations look similar but require different thinking.
How to Fix It
A number line can make negative numbers easier to understand.
For -3 + 8, start at -3 and move eight places to the right. You finish at 5.
For -3 - 8, start at -3 and move eight places to the left. You finish at -11.
Practising these movements helps students connect the calculation to what is happening with the numbers.
Once they understand the basic idea, they can move towards calculations involving multiplication, division and algebraic expressions.
If your child repeatedly struggles with number operations, it may be worth revisiting earlier concepts before moving to more advanced topics.
High Hopes Tutoring Centre offers Maths tutoring in Canning Vale, with lessons covering number skills, mathematical reasoning and problem-solving.
3. Adding Fractions Incorrectly
Fractions are another area where students can make simple but repeated mistakes.
Consider this question:
1/2 + 1/4 = ?
A common incorrect approach is adding the numerators and denominators separately:
1/2 + 1/4 = 2/6
That's incorrect.
To add these fractions, students first need a common denominator.
Correct working:
1/2 = 2/4
2/4 + 1/4 = 3/4
The correct answer is 3/4.
Understanding fractions is important because the same skills are used when working with percentages, ratios and algebraic fractions.
How to Fix It
Use visual examples before moving to more difficult calculations.
For instance, draw a rectangle divided into four equal parts.
Shade two parts to represent one-half, then shade one more part to represent one-quarter.
The student can see that three out of four parts are now shaded.
You can also use everyday examples such as dividing a pizza or measuring ingredients.
The aim is to help your child understand what fractions represent, rather than rely entirely on memorised steps.
4. Forgetting to Apply Algebra Rules Correctly
Algebra becomes a bigger part of Maths as students progress through high school.
It introduces letters to represent unknown numbers, which can initially feel unfamiliar.
One common mistake involves expanding brackets.
For example:
3(x + 2)
A student might write:
3x + 2
But the correct answer is:
3x + 6
Why?
Because the 3 must multiply both terms inside the brackets.
3 × x = 3x
3 × 2 = 6
Therefore:
3(x + 2) = 3x + 6
How to Fix It
Encourage your child to write out the individual multiplication steps.
A simple way to check the answer is to substitute a number for x.
For example, let x = 2.
Original expression:
3(2 + 2) = 12
Expanded expression:
3(2) + 6 = 12
Both give the same result.
If the answers don't match, the student knows they need to review their working.
This checking technique can be useful when learning algebraic expressions.
For students who are finding algebra increasingly difficult, secondary school tutoring at High Hopes provides additional Maths learning support for students in Years 7–10.
5. Misreading Maths Word Problems
Sometimes students understand the calculations but struggle when a question is written as a real-life problem.
This often happens because they rush into calculating before understanding what the question is asking.
For example:
A rectangular garden is 5 metres long and 3 metres wide. What is its area?
A student might add the two measurements instead of multiplying them.
The correct calculation is:
Area = Length × Width
5 × 3 = 15
Answer: 15 square metres
But if the question asked for the perimeter, the method would be different.
Perimeter = 2 × (Length + Width)
2 × (5 + 3) = 16 metres
The measurements are the same, but the questions require different calculations.
How to Fix It
Teach your child to follow a simple process before calculating:
- Read the question carefully.
- Identify what needs to be calculated.
- Highlight the important information.
- Choose the appropriate mathematical method.
- Check whether the answer and units make sense.
Encourage students to draw a quick diagram when it helps.
For geometry questions, a simple sketch can make the problem easier to understand.
For other word problems, writing down the known information and the unknown quantity can help students decide what to do next.
How Can Parents Help Their Child Improve in Maths at Home?
You don't need to be a Maths expert to support your child's learning.
Start by asking which topics they find difficult rather than focusing only on their latest marks.
You can encourage your child to explain how they solved a question. This often reveals whether they understand the method or are simply following memorised steps.
A short, focused practice session can be more manageable than trying to complete a large number of questions at once.
For example, you could set aside 10–15 minutes to revisit one concept, work through two or three questions and discuss any mistakes.
If your child gets an answer wrong, ask them to identify where their working changed direction.
You can also encourage them to keep a small notebook of mistakes, recording the original question, the error and the correct method.
Over time, this can help make recurring difficulties easier to recognise.
When Should You Consider Maths Tutoring?
One disappointing test result doesn't necessarily mean your child needs tutoring.
However, if the same difficulties keep appearing, additional guidance may be useful.
For example, your child may:
- Understand Maths during class but struggle to apply it independently.
- Repeatedly make errors with fractions or algebra.
- Find multi-step problems difficult.
- Need more time to understand new concepts.
- Avoid Maths homework because they don't know where to begin.
Start by discussing these difficulties with your child's classroom teacher.
If additional support is appropriate, tutoring can provide opportunities to revisit specific concepts, practise questions and receive feedback.
For more guidance, read our article on when your teen should start high school tutoring.
Maths Tutoring for High School Students in Canning Vale
High Hopes Tutoring Centre provides academic support for students in Canning Vale, Perth.
The centre's Maths tutoring program focuses on helping students develop their understanding of mathematical concepts and strengthen their problem-solving skills.
Its secondary school program supports students in Years 7–10, covering areas including number and algebra, numerical reasoning and geometry.
Students can access small-group learning and personalised tutoring options, depending on their needs.
The aim is to give learners opportunities to understand difficult concepts, ask questions and practise the skills they need for schoolwork.
For families looking for high school tutoring in Canning Vale, High Hopes offers a free trial class so parents and students can explore the learning environment before enrolling.
Help Your Child Build Stronger Maths Skills
Making mistakes is part of learning Maths. What matters is understanding why they happened and learning how to approach similar questions next time.
If your child is finding fractions, algebra or mathematical problem-solving difficult, additional support may help them work through those areas.
High Hopes Tutoring Centre provides Maths and secondary school tutoring in Canning Vale, with learning options suited to different student needs.
Book a Free Trial Class Today
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High Hopes Tutoring Centre
Suite 18/2 Batman Road, Canning Vale WA 6155
Phone: 0404 497 732
Website: www.highhopestutoring.com.au
Frequently Asked Questions
What are the most common Maths mistakes in high school?
Common mistakes include using the wrong order of operations, errors with negative numbers, incorrect fraction calculations, mistakes when expanding algebraic expressions and misunderstanding word problems.
How can I help my teenager improve in Maths?
Identify the topics they find difficult, encourage them to show their working and practise specific skills regularly. Speak with their classroom teacher if the same problems continue.
Why does my child understand Maths but make mistakes in tests?
There can be several reasons, including rushing, misreading questions, forgetting a method or having gaps in earlier learning. Reviewing their actual working can help identify the cause.
Can tutoring help students struggling with algebra?
Maths tutoring can give students additional opportunities to revisit algebraic concepts, work through examples and receive feedback on mistakes.
Does High Hopes Tutoring provide Maths support for Years 7–10?
Yes. High Hopes Tutoring Centre offers secondary school Maths support for students in Years 7–10 in Canning Vale, Perth.