Understand the idea.
Read the whole timetable
Find the activity row and read its start and finish columns carefully. A start time locates an event in the day; a duration measures how long it lasts. They answer different questions.
Count forward in minutes to find duration. From 09:15 to 10:00 is 45 minutes, then five more reaches 10:05. Art club therefore lasts minutes, rather than a whole hour.
| Activity | Starts | Finishes |
|---|---|---|
| Art club | 09:15 | 10:05 |
| Chess | 10:20 | 11:00 |
| Lunch break | 12:10 | 12:50 |
| Drama | 13:05 | 14:00 |
Allow time between events
A gap between activities must also cover walking, packing or waiting. From 10:05 to 10:20 there are 15 minutes, so an 18-minute walk will not fit. Include every required part of a plan.
For a latest departure, work backwards from the required arrival time. Across midnight, count to 00:00 and continue into the next day. Clock minutes regroup at 60, so subtracting displayed digits as ordinary decimals is unreliable.
See the method in action.
Find duration
How long does Drama last?
| Activity | Starts | Finishes |
|---|---|---|
| Art club | 09:15 | 10:05 |
| Chess | 10:20 | 11:00 |
| Lunch break | 12:10 | 12:50 |
| Drama | 13:05 | 14:00 |
Worked solution
- 1
Read Drama start and finish.
The Drama row supplies both times on the same day.
- 2
Count the minutes to the next hour.
13:05 is five minutes into the hour, leaving 55 minutes before 14:00.
- 3
Check the finishing time.
The counted duration reaches the timetable finish exactly.
55 minutes
Plan backwards
A bus leaves at 15:40. Walking to the stop takes 12 minutes. You want to arrive 5 minutes early. When should you leave?
Worked solution
- 1
Find the required arrival time.
Arriving five minutes early means being at the stop before the bus leaves.
- 2
Allow the walk before arrival.
The twelve-minute walk must finish by 15:35.
- 3
Check forwards from departure.
Leaving at 15:23, or 3:23 pm, allows both the walk and the five-minute wait.
15:23, or 3:23 pm
Try it yourself.
Check your understanding
A lesson begins at 11:40 and ends at 12:15. How long is it?
Show answer & reasoning
35 minutes
Count 20 minutes from 11:40 to noon, then 15 minutes to 12:15. The total is minutes.
Keep practising
6 worksheet questions · 10 marks
Read the questions online
- Use the timetable. When does Chess start in 12-hour time?1 mark
Community centre timetable Activity Starts Finishes Art club 09:15 10:05 Chess 10:20 11:00 Lunch break 12:10 12:50 Drama 13:05 14:00 - Use the timetable. How long is the Lunch break?1 mark
Community centre timetable Activity Starts Finishes Art club 09:15 10:05 Chess 10:20 11:00 Lunch break 12:10 12:50 Drama 13:05 14:00 - A train leaves at 14:35 and arrives at 15:20 on the same day. Find the journey time.2 marks
- A film starts at 17:50 and lasts 1 hour 35 minutes. When does it finish?2 marks
- A game ends at 16:25. A bus leaves at 16:40. Walking to the stop takes 18 minutes. Can you catch it if you leave as the game ends? Explain.2 marks
- A ferry leaves at 23:45 and arrives at 00:20 the next day. Find its travel time.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Use the timetable. When does Chess start in 12-hour time?1 mark
Community centre timetable Activity Starts Finishes Art club 09:15 10:05 Chess 10:20 11:00 Lunch break 12:10 12:50 Drama 13:05 14:00 10:20 is before noon.
10:20 am - Use the timetable. How long is the Lunch break?1 mark
Community centre timetable Activity Starts Finishes Art club 09:15 10:05 Chess 10:20 11:00 Lunch break 12:10 12:50 Drama 13:05 14:00 12:10 to 12:50 is 40 minutes.
40 minutes - A train leaves at 14:35 and arrives at 15:20 on the same day. Find the journey time.2 marks
25 minutes to 15:00, then 20 more: .
45 minutes - A film starts at 17:50 and lasts 1 hour 35 minutes. When does it finish?2 marks
Add 1 hour to get 18:50, then add 35 minutes.
19:25, or 7:25 pm - A game ends at 16:25. A bus leaves at 16:40. Walking to the stop takes 18 minutes. Can you catch it if you leave as the game ends? Explain.2 marks
.
No; you arrive at 16:43, three minutes after departure. - A ferry leaves at 23:45 and arrives at 00:20 the next day. Find its travel time.2 marks
15 minutes to midnight and 20 after it: .
35 minutes
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum Mathematics 2026
12-/24-hour clocks; conversion; interpreting schedules.
Official curriculum source ↗