The idea, step by step
Use useful jumps
Duration means how long something lasts. Start at the beginning time and count forward to the finish.
An easy first jump is to the next hour. From 10:45 to 11:00 is 15 minutes.
Keep track of each part
From 10:45 to 11:20, count 15 minutes to 11:00 and 20 more minutes to 11:20. The total duration is 35 minutes.
For a finish time, remember the minutes start again at zero after 59. Thirty minutes after 3:45 is 4:15.
A common trap
Treating clock times like ordinary decimal numbers.
Instead: Count through each hour using 60 minutes.
See the thinking
Reading time
A class reads from 11:10 to 11:35. How long is that?
- The hour does not change.
- 35 − 10 = 25 minutes.
A game crosses the hour
A game starts at 2:50 and lasts 25 minutes. When does it finish?
- Ten minutes takes the time to 3:00.
- There are 15 minutes still to add.
Check your understanding
How long is it from 9:55 to 10:05?
Show answer
10 minutes
Five minutes to 10:00, then five more minutes.
Your turn
6 questions · Work at your own pace.
Read the questions online
- A lesson starts at 9:15 and ends at 9:40. Find its duration.
- A bus leaves at 1:45 and arrives at 2:10. How long is the trip?
- A game begins at 4:05 and lasts 20 minutes. Find the finish time.
- A cake goes in the oven at 10:40 for 30 minutes. When is it ready?
- Which lasts longer: 8:20 to 8:50, or 1:10 to 1:35?
- A train leaves at 3:30 and arrives at 4:30. A child says it takes 100 minutes. Correct the answer.
Read the worked solutions
- A lesson starts at 9:15 and ends at 9:40. Find its duration.
Count forward from 15 past to 40 past.
25 minutes - A bus leaves at 1:45 and arrives at 2:10. How long is the trip?
15 minutes to 2:00 and 10 more minutes make 25.
25 minutes - A game begins at 4:05 and lasts 20 minutes. Find the finish time.
Add 20 minutes to 4:05.
4:25 - A cake goes in the oven at 10:40 for 30 minutes. When is it ready?
20 minutes to 11:00 and 10 more minutes.
11:10 - Which lasts longer: 8:20 to 8:50, or 1:10 to 1:35?
The durations are 30 minutes and 25 minutes.
8:20 to 8:50, by 5 minutes. - A train leaves at 3:30 and arrives at 4:30. A child says it takes 100 minutes. Correct the answer.
The times are exactly one hour apart.
An hour contains 60 minutes.
60 minutes, or 1 hour.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum
Analogue/digital clocks to the minute; seconds/minutes/hours/days; duration.
Official curriculum source ↗