IGCSE Mathematics: Time Practice Questions
Time is not decimal. There are 60 minutes in an hour, so 2.5 hours is 2 hours 30 minutes and 2.4 hours is 2 hours 24 minutes, not 2 hours 40 minutes.
Topic 1.14 of Cambridge IGCSE Mathematics 0580 is short but costs marks in speed and distance questions throughout the paper. The decimal conversion is the trap, and it appears more often than any pure time question. The questions below make you handle it directly.
What you need to know for Time
- 24-hour clockWritten with four digits, so 2:35 pm is 14:35. Midnight is 00:00 and midday is 12:00.
- DurationCount on in whole hours first, then add the remaining minutes. Working forwards avoids borrowing errors.
- Decimal hours to hours and minutesMultiply the decimal part by 60. So 2.4 hours is 2 hours plus 0.4 x 60 = 24 minutes.
- Hours and minutes to decimal hoursDivide the minutes by 60. So 2 hours 45 minutes is 2 + 45 divided by 60 = 2.75 hours.
- Crossing midnightCount up to 24:00, then continue from 00:00. Add a day to the date if the question asks for it.
- Using time in speed calculationsSpeed in km per hour requires time in decimal hours. Convert before substituting.
IGCSE Mathematics Time questions and answers
4 exam-style questions written to the 0580 syllabus. Try each one on paper first, then open the worked answer to check your method against the marks.
A train leaves at 14:35 and arrives at 17:20. Calculate the journey time.
Show the worked answer
- Count forwards in whole hours first: 14:35 to 16:35 is 2 hours.
- From 16:35 to 17:00 is 25 minutes.
- From 17:00 to 17:20 is a further 20 minutes, so 25 + 20 = 45 minutes.
- The total journey time is 2 hours 45 minutes.
A car travels 176 km in 2 hours 45 minutes. Calculate its average speed in km per hour.
Show the worked answer
- Speed in km per hour needs the time expressed in decimal hours.
- 45 minutes = 45 divided by 60 = 0.75 hours, so the time is 2.75 hours.
- Speed = distance divided by time = 176 divided by 2.75.
- Speed = 64 km/h.
A bus leaves at 22:40 and the journey takes 5 hours 35 minutes. Calculate the arrival time and state whether it arrives on the same day.
Show the worked answer
- Add the whole hours first: 22:40 plus 5 hours = 03:40, which has passed midnight.
- Add the remaining 35 minutes: 03:40 plus 35 minutes = 04:15.
- Since the clock passed 24:00 during the journey, the arrival is on the following day.
- The bus arrives at 04:15 the next day.
Convert 2.4 hours into hours and minutes, and explain why the answer is not 2 hours 40 minutes.
Show the worked answer
- The whole number part gives 2 hours.
- The decimal part, 0.4, is a fraction of an hour, not a number of minutes.
- Multiply by 60 to convert it: 0.4 x 60 = 24 minutes.
- So 2.4 hours is 2 hours 24 minutes. It is not 2 hours 40 minutes, because an hour has 60 minutes rather than 100, so 0.4 of an hour is 24 minutes, not 40.
Common mistakes in this topic
- Treating the digits after a decimal point as minutes.
- Subtracting times on a calculator as though they were decimals.
- Writing a time beyond 24:00 instead of resetting past midnight.
- Forgetting to convert minutes to decimal hours before a speed calculation.
- Using am and pm in a 24-hour clock answer.
Exam tips
- Count forwards in whole hours first, then add the minutes. It avoids borrowing entirely.
- Decimal to minutes: multiply by 60. Minutes to decimal: divide by 60.
- Any speed question in km per hour needs the time in decimal hours.
- Write 24-hour times with four digits, so 09:05 rather than 9:05.
- If a journey crosses midnight, say which day the arrival falls on.
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Time FAQs
Why is 2.4 hours not 2 hours 40 minutes?
Because an hour contains 60 minutes, not 100. The decimal 0.4 represents four tenths of an hour, which is 0.4 multiplied by 60, giving 24 minutes. So 2.4 hours is 2 hours 24 minutes.
How do I convert minutes into decimal hours?
Divide the number of minutes by 60. So 45 minutes is 45 divided by 60, which is 0.75 hours, making 2 hours 45 minutes equal to 2.75 hours. This conversion is essential before any speed calculation in kilometres per hour.
How do I calculate a journey time across midnight?
Count forwards from the departure time to 24:00, then continue from 00:00 to the arrival time, adding the two parts. Note that the arrival falls on the following day, and never write a time greater than 24:00.
How do I work out a duration between two 24-hour times?
Count on in whole hours from the start time until you are within an hour of the finish, then add the remaining minutes. Subtracting the two times directly on a calculator treats them as decimals and gives a wrong answer.
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Written to the published Cambridge IGCSE Mathematics (0580) syllabus. Check your school entry code and syllabus year, because Core and Extended candidates are assessed on different content. Last reviewed 2026-08-12.