Primary 1 maths · Measurement & time · About 8 minutes
Find durations of one hour or half an hour
Start at the given time. Count on.
Start the interactive lesson →Open practice activity
What you will learn
- Find durations of one hour or half an hour
Models used: number sentences, stories, diagrams.
Before you start
Jump to the next hour first
An activity starts at 9:45. We want to go forward by 30 minutes.
The dots are times of day. Each curved arrow is a number of minutes passing.
An activity starts at 9:45. We want to go forward by 30 minutes.
Split a long wait into easier jumps. Add the durations of the jumps, not the clock readings at their ends.
The dots are times of day. Each curved arrow is a number of minutes passing.
First use 15 minutes to reach 10 o’clock.
Split a long wait into easier jumps. Add the durations of the jumps, not the clock readings at their ends.
The dots are times of day. Each curved arrow is a number of minutes passing.
There are 15 minutes still to use. Another jump takes us to 10:15.
15 + 15 = 30 minutes
Split a long wait into easier jumps. Add the durations of the jumps, not the clock readings at their ends.
What did the picture help us see?
There are 15 minutes still to use. Another jump takes us to 10:15.
Worked example: A new example, together
An activity starts at 2:20 pm and lasts 60 minutes. When does it end?
Start at the given time. Count on.
A duration is the time between the start and finish. Move forward from the start, or backwards from the finish, by that duration.
Start time. Move ahead 60 minutes. Use the relationship: start time + duration = finish time.
Start time. Move ahead 60 minutes. An activity starts at 2:20 pm and lasts 60 minutes. When does it end?
3:20 pm
Move forward by the duration.
Start time. Move ahead 60 minutes. 2:20 pm + 60 minutes = 3:20 pm.
Start time. Move ahead 60 minutes. Check the result against the question we started with.
3:20 pm minus 60 minutes returns to 2:20 pm.
We found 3:20 pm. A duration is the time between the start and finish. Move forward from the start, or backwards from the finish, by that duration.
Start time. Move ahead 60 minutes.
Common mistakes to discuss
- Writing a time past sixty. Count on to the next hour, then add what is left. 9:45 plus 30 minutes is 10:15, never 9:75.
Check your understanding
- Find durations of one hour or half an hour
- find a later time
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
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