The idea, step by step
Read the whole timetable
A timetable joins an event to a start or finish time. Find the correct row and column, then check whether times use the 24-hour system. A start time is not the length of the activity.
To find duration, count forward to a convenient hour and then the finish. Art club lasts 45 minutes to 10:00 and 5 more minutes to 10:05: 50 minutes altogether.
| 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 free gap must cover packing, waiting and travelling. Between Art club ending at 10:05 and Chess starting at 10:20 there are 15 minutes. An 18-minute walk would not fit.
If the finish is after midnight, name the next day and count across 24:00/00:00. Do not subtract displayed hour numbers without thinking about the day.
A common trap
13:50 to 14:10 is 60 minutes because the hour number changes.
Instead: Count minutes: 10 to 14:00 and 10 more to 14:10 gives 20 minutes.
See the thinking
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 |
- 13:05 to 14:00 is 55 minutes.
- Both times are on the same day.
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?
- Arrive by 15:35.
- Count back 12 minutes: 15:35 − 12 minutes = 15:23.
Check your understanding
A lesson begins at 11:40 and ends at 12:15. How long is it?
Show answer
35 minutes
There are 20 minutes to noon, then 15 more.
Your turn
6 questions · 10 marks · Work at your own pace.
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: 25 + 20 = 45.
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
16:25 + 18 minutes = 16:43.
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: 15 + 20 = 35.
35 minutes
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum Mathematics 2026
12-/24-hour clocks; conversion; interpreting schedules.
Official curriculum source ↗