How to Ace IGCSE Mathematics Paper 1: Non-calculator (Core)

That moment before you turn the page

You're sitting in the exam hall. Your pencil is sharp, your eraser is ready, and your calculator is... nowhere. It's Paper 1, and every answer has to come from your own working. If that thought makes your stomach flip, you're not alone. But here's the reassuring truth: this paper is designed to be done without a calculator. The numbers are chosen to work out neatly. The examiners aren't trying to catch you out with impossible arithmetic. They're testing whether you understand the method, and whether you can show it clearly on the page.

Your job over the next 60 minutes is straightforward. Work through 56 marks of short-answer questions, show your reasoning at every step, and collect marks for method even when the final number slips away from you. That last point is worth repeating: you can score marks for working even if your answer is wrong. Understanding how the mark scheme rewards you is half the battle.

What the paper looks like

Paper 1 is the non-calculator paper for the Core tier, which means grades C through G are available. The questions are short-answer style, printed in a booklet with space for your working and your answer. They start easy and get progressively harder, so the first few questions might feel almost too simple. That's deliberate. Those early marks are yours for the taking, and you should collect every single one.

Time management: your 60-minute game plan

With 56 marks in 60 minutes, you've got just over a minute per mark. That sounds tight, but many early questions take less than a minute each, which builds you a time buffer for the harder questions near the end.

Here's a rough breakdown that works well in practice:

1. Minutes 1-20: Work through the first third of the paper. These tend to be 1- and 2-mark questions on basic skills: arithmetic, reading values, simple angles. Aim to finish these quickly but carefully. Don't rush so fast that you make silly errors, but don't overthink either.
2. Minutes 20-40: The middle section. Questions here are worth 2-4 marks and require more working. This is where you'll see fractions, percentages, area and perimeter, basic algebra, and data interpretation. Show every step.
3. Minutes 40-55: The final questions are the hardest and carry the most marks. If you get stuck, write down what you do know and move on. Come back with fresh eyes if there's time.
4. Minutes 55-60: Check your work. Read each answer back against the question. Did they ask for centimetres and you gave metres? Did they want a fraction and you left a decimal? These small corrections can rescue marks.

How the mark scheme actually works

Understanding mark types is one of the most powerful things you can do for your score. IGCSE Mathematics mark schemes use three types of marks:

• M marks (method): Awarded for using a correct approach, even if you make a calculation error along the way. Writing "180 - 65 - 48" for finding a missing angle in a triangle earns the method mark whether your subtraction is right or not.
• A marks (accuracy): Awarded for a correct answer, usually following from correct method. You typically can't earn an A mark without the M mark that comes before it.
• B marks (independent): Awarded for a correct statement or answer that doesn't depend on previous working. Things like stating a definition, reading a value from a graph, or writing down a formula.

What does this mean in practice? It means your working is worth marks. If a question is worth 3 marks and you set up the correct equation (1 M mark), substitute correctly (1 M mark), but make an arithmetic slip at the end, you still collect 2 out of 3. That's a huge difference from leaving the page blank.

Non-calculator arithmetic: the skills that matter

You won't be asked to multiply 4,739 by 683 in your head. The numbers in Paper 1 are chosen to be workable. But you do need to be confident with certain mental and written methods. Here are the ones that come up most often.

Fractions

Adding and subtracting fractions with different denominators is one of the most commonly tested skills on this paper. The method is always the same: find a common denominator, convert both fractions, then add or subtract the numerators.

Worked example: Calculate 3/4 + 2/5

1. Common denominator of 4 and 5 is 20
2. 3/4 = 15/20
3. 2/5 = 8/20
4. 15/20 + 8/20 = 23/20 = 1 3/20

If the question says "give your answer as a mixed number," don't leave it as 23/20. Read the question carefully.

Percentages without a calculator

The trick is to build from easy percentages you can find in your head:

• 50% = divide by 2
• 10% = divide by 10
• 5% = half of 10%
• 1% = divide by 100

From those four building blocks, you can construct almost any percentage. Need 35% of 240? That's 10% + 10% + 10% + 5% = 24 + 24 + 24 + 12 = 84.

Long multiplication and division

You might need to multiply two- or three-digit numbers. Use the grid method or column method, whichever you're most comfortable with. The important thing is to write out the steps clearly. If the examiner can follow your working, they can award method marks even if you slip up at the end.

Topic-by-topic strategies

Number questions

These appear throughout the paper, from the very first question to the middle section. You'll see questions on place value, ordering decimals, factors and multiples, squares and cubes, fractions, percentages, ratio, and estimation. For estimation questions, remember to round each number to 1 significant figure before calculating. Show the rounded values clearly so the examiner can see your method.

Algebra questions

At Core level, algebra stays relatively straightforward. You'll be asked to simplify expressions (collect like terms), expand single brackets, substitute values into formulas, and solve simple linear equations. The most common mistake is sign errors. When you expand -3(2x - 5), remember that the negative sign multiplies both terms: -6x + 15, not -6x - 15.

Worked example: Solve 4x + 7 = 23

1. 4x + 7 = 23
2. 4x = 23 - 7 = 16
3. x = 16/4 = 4

Write each step on a new line. The examiner needs to follow your chain of reasoning.

Geometry questions

Angle questions are almost guaranteed. Know your angle facts cold: angles on a straight line add to 180, angles at a point add to 360, vertically opposite angles are equal, angles in a triangle add to 180. When you use an angle fact, state which one. Writing "angles on a straight line" next to your calculation picks up reason marks that many students leave on the table.

For area and perimeter, write the formula first, then substitute. Even if the question doesn't say "show your working," a 2- or 3-mark question expects to see the formula and substitution, not just a bare number.

Statistics and probability

You might be asked to calculate a mean from a list or frequency table, read a bar chart or pie chart, describe a correlation on a scatter diagram, or find simple probabilities. For the mean from a frequency table, set up a clear column showing each value multiplied by its frequency, then divide the total by the sum of frequencies. Laying this out in a mini table keeps your working tidy and makes errors easier to spot.

The five mistakes that cost the most marks

"Show that" questions: a special case

Some questions give you the answer and ask you to prove it. These trip students up because they think the work is done since the answer is already on the page. It's not. In a "show that" question, every single step of working must be visible. You need to start from the information given, show each calculation clearly, and arrive at the stated answer with no jumps or gaps.

Think of it like explaining to a friend who missed the lesson. They need to see how you got from A to B, not just that B is true. If the question says "Show that the area is 45 cm squared," and you just write "Area = 45," you'll earn zero marks even though the number is correct.

Your six-week past paper plan

Past papers are the single best revision tool for this exam. Here's a simple plan that builds your confidence steadily.

1. Weeks 1-2 (untimed, open book): Do two past papers per week. Keep your notes open. Focus on understanding the method for every question. When you get something wrong, don't just read the mark scheme. Redo the question from scratch until you can get it right on your own.
2. Weeks 3-4 (timed, open book): Do two past papers per week under timed conditions (60 minutes). You can still check your notes if stuck, but the clock is running. This trains your time awareness.
3. Weeks 5-6 (full exam conditions): Do two or three papers per week. No notes, no calculator, strict 60-minute timing. Mark them honestly using the mark scheme. Track your score out of 56 and aim to see improvement each paper.

On exam day

Bring at least two sharp pencils, an eraser, and a ruler. You don't need a calculator for this paper, so leave it in your bag to avoid any confusion. Read every question twice before you start writing. Check whether they want a specific unit, a specific form (fraction, decimal, percentage), or a specific number of significant figures or decimal places.

If you finish early, don't just sit there feeling relieved. Go back through your paper. Check arithmetic by doing it again from scratch rather than just re-reading what you wrote, because re-reading tends to confirm the original mistake. Pay special attention to questions where you felt uncertain. A fresh pair of eyes, even if they're your own, can catch errors that a tired brain glossed over the first time.

You've practised the methods. You know how the mark scheme works. You've got 60 minutes and a sharp pencil. That's genuinely all you need for this paper. Trust your preparation, show your working, and pick up every mark you can.