Enter calculations and interpret calculator displays
Choose a suitable calculator entry, keep unrounded values through multi-step work and interpret decimal displays in context.
Section 1 · Number
Use this pathway for Cambridge IGCSE International Mathematics 0607, 2028–2030. Core and Extended objectives are labelled in each lesson; Extended adds requirements beyond Core. Paper 1 and Paper 2 are non-calculator. Papers 3–6 require a graphic display calculator (GDC). These original lessons use self-checked practice; they are not a Cambridge grade, full timed paper or teacher review.
Before you begin
- Check whether your school has entered you for Core or Extended. Core and Extended share most Number ideas, but some notation and methods are Extended only.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which decimal represents 2 hours 30 minutes?
What you will learn
- Enter expressions with brackets and mixed units correctly
- Retain calculator precision until the final answer
- Read calculator decimals as money, time or other contextual quantities
Make the written expression match the intended calculation
Use brackets to show a whole numerator or denominator, a repeated percentage multiplier, or a converted time. Check whether the calculator needs a mixed number entered as a fraction or decimal.
For example, 2 hours 30 minutes is 2.5 hours, not 2.30 hours. A decimal entry of $4.8 means $4.80, while a time entry of 3.25 hours means 3 hours 15 minutes.
Keep precision and round once
Do not round a displayed intermediate result if it will be used in a later part. Keep the calculator value and round only the final answer to the requested accuracy.
A graphic display calculator is required for Papers 3–6. Paper 1 and Paper 2 are non-calculator. Across the GDC papers, candidates should be able to sketch a graph, make a table, plot points and find zeros, extrema and intersections; Extended candidates also use linear regression.
Pause and explain
When should you round a multi-step calculator result?
Worked example
A journey lasts 2 hours 30 minutes at 48 km/h. Enter the duration in hours and find the distance.
Show the worked solution
- Convert 30 minutes to half an hour, so the duration is 2.5 hours.
- Enter 48 × 2.5, using the whole duration as the time factor.
- The result is 120 km.
Answer Enter 2.5 hours; distance is 120 km.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A calculation is 36.75 ÷ 2.5. Find the exact calculator value and state it to 3 significant figures.
Give me a hint
Enter the full expression, then round the result only after division.
Compare my reasoning
- Enter 36.75 ÷ 2.5.
- The calculator value is 14.7.
- 14.7 already has 3 significant figures.
14.7.
Look for these in your work
- Division entered in the right order
- No unnecessary intermediate rounding
- Significant figures counted correctly
A receipt shows $4.8 and a timer shows 3.25 hours. Interpret both quantities in ordinary context.
Give me a hint
Money uses cents; convert the fractional hour into minutes.
Compare my reasoning
- $4.8 means $4.80.
- 0.25 hour × 60 = 15 minutes.
- So 3.25 hours is 3 hours 15 minutes.
$4.80 and 3 h 15 min.
Look for these in your work
- Money display interpreted
- Fractional hour converted
- Context attached to each value
A final answer must be given to 3 significant figures. The calculator shows 0.00678291 after several steps. Give the rounded answer and explain what should be stored for the next part.
Give me a hint
Count significant figures from the first non-zero digit; use the unrounded display for follow-on work.
Compare my reasoning
- The first three significant digits are 6, 7 and 8.
- The next digit is 2, so the 8 stays unchanged.
- Report 0.00678, but keep 0.00678291 for any later calculation.
Report 0.00678; retain 0.00678291 internally for subsequent parts.
Look for these in your work
- Leading zeros not counted
- Rounding digit checked
- Intermediate precision retained
Common mistakes
- Entering 2.30 hours for 2 h 30 min
- Rounding an intermediate display
- Leaving out brackets around a denominator
- Using a calculator in a non-calculator paper
What can you explain now?
How many hours is 3 hours 15 minutes as a decimal?
Compare with the explanation
3.25 hours
15 minutes is one quarter of an hour.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
What should you check before pressing equals, and why should an intermediate calculator display stay unrounded?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.