6.1 Calculate time difference
You may need to work out differences in time, e.g. to work out the length of a TV programme or journey time.
There are different ways to work out the difference in time. One of the easiest ways is to use the adding on method.
Example: Time difference by adding on
How long is it from 08:45 to 10:30?
Method
The start time is 08:45.
The number of minutes between 08:45 and the start of the next hour, 09:00, is 15 minutes.
The number of hours between 09:00 and 10:00 is one hour.
The number of minutes between 10:00 and 10:30 is 30 minutes.
So the time between 08:45 to 10:30 is:
15 minutes + 30 minutes + 1 hour = 1 hour 45 minutes
Now try the following activity.
Activity 21: Time difference
What is the length of time between the following times?
- 03:55 to 06:35
- 09:45 to 12:15
- 08:26 to 10:14
- 7:55 a.m. to 1:10 p.m.
- Midday to 15:50
- 3:15 am to midnight
Answer
-
The start time is 03:55.
The number of minutes between 03:55 and the start of the next hour, 04:00, is 5 minutes.
The number of hours between 04:00 and 06:00 is two hours.
The number of minutes between 06:00 and 06:35 is 35 minutes.
So the time between 03:55 to 06:35 is:
- 5 minutes + 35 minutes + 2 hours = 2 hours 40 minutes
-
The start time is 09:45.
The number of minutes between 09:45 and the start of the next hour, 10:00, is 15 minutes.
The number of hours between 10:00 and 12:00 is two hours.
The number of minutes between 12:00 and 12:15 is 15 minutes.
So the time between 09:45 to 12:15 is:
- 15 minutes + 15 minutes + 2 hours = 2 hours 30 minutes
Following the same method, you should have these answers for the other questions:
- 1 hour 48 minutes
- 5 hours 15 minutes
- 3 hours 50 minutes
- 20 hours 45 minutes