Cambridge 0580 answer checks
When should you round an IGCSE Maths answer?
Keep precision during the calculation and round when presenting the final answer. First check the question: an exact value, a specified accuracy and a general paper instruction are different requirements.
Start with the course code and the instruction
This guide concerns Cambridge IGCSE Mathematics 0580 for examinations in 2025 to 2027, checked on 19 October 2026. Its calculator-paper guidance asks for non-exact numerical answers to three significant figures, or one decimal place for angles in degrees, unless the question specifies otherwise. That is not a universal rule for every subject, board or future syllabus.
Read the individual question before applying a default. If it asks for two decimal places, use two decimal places. If it asks for an exact value, a rounded decimal may be the wrong form. Cambridge also says not to round answers that are already exact to four or five significant figures unless instructed. Precision is a decision about the task, not a habit of shortening every number.
The hero image is generated and shows fictional people, not an actual lesson or teacher. All numerical examples below are original practice, not past-paper questions or recorded pupil results.
Count significant figures from the first non-zero digit
Consider 0.004786. To round to three significant figures, start counting at 4: keep 4, 7 and 8, then inspect the next digit, 6. The result is 0.00479. The leading zeros locate the decimal point; they are not the first significant figures. By contrast, rounding the same number to three decimal places gives 0.005.
Now consider 12.306. To two decimal places it is 12.31; to three significant figures it is 12.3. Ask the student to mark the last digit being kept before deciding whether it changes. This separates counting from rounding, making it easier to identify which part went wrong.
Zeros inside a number count. A trailing zero in a decimal answer can also communicate the requested accuracy: 4.50 to three significant figures is not written the same way as 4.5 to two significant figures. Avoid erasing that useful information during the final check.
| Starting value | Instruction | Answer |
|---|---|---|
| 0.004786 | 3 significant figures | 0.00479 |
| 0.004786 | 3 decimal places | 0.005 |
| 12.306 | 2 decimal places | 12.31 |
| 12.306 | 3 significant figures | 12.3 |
See what happens when a middle step is shortened
Use an invented calculation: multiply the square root of 7 by 19 and give the final result to three significant figures. Keeping the calculator value of the square root gives approximately 50.269275, which rounds to 50.3. If the square root is shortened to 2.65 first, the next multiplication gives 50.35, which rounds to 50.4.
Both routes look tidy on paper, but early rounding has changed the requested answer. Keep the stored calculator value, or use the full expression in a single calculation, while writing enough working to show the method. A rounded value written for communication should not silently replace the more precise value needed in the next step.
The same issue appears across parts of a question. If part (b) uses a quantity found in part (a), Cambridge tells candidates to use its unrounded value. Preserve the expression or calculator memory where appropriate. Do not assume that copying the displayed final answer from the answer line is always the most accurate way to continue.
Keep exact values exact when the task asks for them
A circle with a specified radius of 5 cm has area 25π cm² in an exact mathematical calculation. If the task requests an answer in terms of π, replacing that with 78.5 cm² changes its form and loses exactness. A fraction such as 2/3 and a surd such as the square root of 7 can also be exact forms. The decimal approximation is useful only when the task calls for it.
Do not confuse an exact mathematical value with a physical measurement that has limited accuracy. Read the problem context. When comparing an answer with a mark scheme, first check whether the difference is notation, rounding or an incorrect method; they need different repairs.
This generated study-material illustration contains no reference calculation. The worked values in the text and table are the information to check.
Use a four-part check before moving on
Read the required form; identify the final value; apply the accuracy instruction once; then check the units. A correct numerical result can still be unclear if an area is labelled in centimetres rather than square centimetres. If the question is about an angle, check the angle unit before applying an accuracy rule for degrees.
Try 8.0964 to three significant figures. Keeping 8, 0 and 9 and looking at the next digit gives 8.10. The carry changes the tenths digit, and the final zero records the third significant figure. Then try the same value to two decimal places: it also gives 8.10, but for a different counting reason. Matching answers do not mean the two instructions are interchangeable.
Use the past-paper practice guide to place these checks inside a complete attempt. The separate command-word examples explain how the task verb changes the kind of answer required; this guide stays with numerical accuracy.
Make the next lesson about the specific error
When asking about Cambridge course support, include the syllabus code, exam year and one attempted calculation. Mark where a value was shortened. That gives an educator something concrete to discuss without treating every lost mark as a general weakness in mathematics.
If your family is based in Uluwatu, the Uluwatu arrangements page is a practical starting point for location and timetable questions. Confirm the exact address and tutor availability before booking. Your current paper instructions and teacher guidance remain the final reference for an assessed task.
Frequently asked questions
Should I round every number to three significant figures?
Round the final non-exact answer as instructed, not every number in the working. Exact answers and explicitly specified accuracy require separate decisions. These Cambridge 0580 conventions should not be transferred automatically to another course.
Why does 8.0964 become 8.10 rather than 8.1?
For three significant figures, 8.10 communicates three counted digits: 8, 1 and the final zero. The value is numerically equal to 8.1, but the written precision matters when the question asks for a particular accuracy.
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