0580
Time, Currency and Conversions
Number
Finding a duration
- Subtracting clock times directly gives a wrong answer, because the columns are not worth ten
- Count on instead: go up to the next whole hour, then in whole hours, then the remaining minutes
- From 14 25 to 18 10: 35 minutes reaches 15 00, then 3 hours reaches 18 00, then 10 minutes more, giving 3 hours 45 minutes
- Adding a duration works the same way, carrying 60 minutes as one hour
Worked example
Finding an arrival time
A train departs at 09 48 and the journey takes 2 hours 37 minutes. Find the arrival time.
Solution:
- Add the hours first: 09 48 plus 2 hours is 11 48
- Add the minutes: 48 + 37 = 85 minutes
- 85 minutes is 1 hour and 25 minutes, so carry the hour
- The train arrives at 12 25
Worked example
Adding a duration to a time
A bus leaves at 14 35 and the journey takes 2 hours 50 minutes. Work out the arrival time.
Solution:
- Add the hours first: 14 35 + 2 hours = 16 35
- Then add the minutes: 35 + 50 = 85 minutes
- 85 minutes is more than an hour, so exchange 60 of them for 1 hour, leaving 25
- 16 35 + 50 minutes = 17 25
- The bus arrives at 17 25
- Adding 2.50 to 14.35 on a calculator gives 16.85, which is not a time at all — minutes are sixtieths, not decimals