Calculate with time, timetables, money and currency
Convert time units and clock formats, solve timetable and time-zone problems, and work with money and exchange rates.
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
What is 2 hours 30 minutes as a number of minutes?
What you will learn
- Convert between seconds, minutes, hours, days, weeks, months and years
- Read 12-hour and 24-hour times and calculate durations
- Calculate with money and currency exchange rates
Convert time using units rather than decimal-looking labels
There are 60 seconds in a minute and 60 minutes in an hour. A year is taken as 365 days in this syllabus. Convert to a single unit before adding or dividing durations.
For a duration across midnight, add the time to midnight and then the remaining time after midnight. A 24-hour time such as 15:15 is 3:15 p.m.; a.m. and p.m. change the date when a journey crosses midnight.
Read currency directions carefully
If 1 unit of currency A buys r units of currency B, multiply an amount in A by r to convert it to B; divide by r to go back. State the currency in each line.
Money is usually rounded to the nearest cent or smallest stated unit. If a fee is charged, apply it in the direction described and do not assume the fee is part of the exchange rate.
Pause and explain
If $1 buys 25 000 dong, how many dong do $4 buy before fees?
Worked example
A coach leaves at 22:45 and travels for 3 hours 38 minutes. Find its arrival time in 24-hour notation.
Show the worked solution
- From 22:45 to midnight is 1 hour 15 minutes.
- Subtract that from the journey duration: 3:38 − 1:15 = 2:23 remaining.
- The remaining time after midnight is 02:23.
Answer Arrival time 02:23 the following day.
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 train departs at 18:47 and arrives at 21:16. Find the journey duration.
Give me a hint
Count to the next hour, then add the remaining minutes.
Compare my reasoning
- 18:47 to 19:00 is 13 minutes.
- 19:00 to 21:00 is 2 hours; 21:00 to 21:16 is 16 minutes.
- 13 + 16 = 29 minutes.
2 hours 29 minutes.
Look for these in your work
- Clock times ordered
- Hours and minutes separated
- Duration totals checked
A student travels from a city at 09:35 local time for 7 hours 50 minutes. The destination is 2 hours ahead. Find the arrival local time.
Give me a hint
Find arrival time in the departure time zone, then add the time-zone difference.
Compare my reasoning
- 09:35 + 7:50 = 17:25.
- Add 2 hours for the destination time zone: 19:25.
- No midnight crossing occurs.
19:25 local time at the destination.
Look for these in your work
- Travel time added
- Time-zone direction checked
- 24-hour time stated
Convert $320 to dong at $1 = 25 400 dong. A service fee of 1.5% is deducted from the dong received. How much arrives, to the nearest 1 000 dong?
Give me a hint
Convert first, calculate the fee as a percentage of the converted amount, then subtract.
Compare my reasoning
- Converted amount is 320 × 25 400 = 8 128 000 dong.
- Fee = 0.015 × 8 128 000 = 121 920 dong.
- Received = 8 006 080 dong, which rounds to 8 006 000 dong to the nearest thousand.
8 006 000 dong to the nearest 1 000 dong.
Look for these in your work
- Exchange direction correct
- Fee applied to converted amount
- Rounding requested unit used
Common mistakes
- Treating minutes as hundredths of an hour
- Forgetting the day changes at midnight
- Multiplying when the stated exchange rate needs division
- Rounding currency before fees or later calculations
What can you explain now?
How many minutes are in 2.4 hours?
Compare with the explanation
144 minutes
Multiply 2.4 by 60.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How do you calculate across midnight, convert time zones and decide whether an exchange rate is multiplied or divided?
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.