The difference between a time and a duration
A clock time is a moment; a duration is the interval between moments. Think separately about hours and minutes instead of subtracting digital times like decimal numbers.
Try it yourself first.
An activity starts at 14:35 and ends at 15:20. Find the time to 15:00 and then to the finish. How many minutes pass altogether?
View the solution or example answer
There are 25 minutes to 15:00, then 20 minutes to 15:20: a total of 45 minutes. An hour has 60 minutes, so ordinary decimal subtraction alone is not suitable.
Your next step.
Mark the start and finish on a timeline. Two smaller steps through the whole hour can make mental calculation easier. Check by adding the duration back to the start.
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