The shape of the lesson
By the end of the lesson, learners can
- 12-hour and 24-hour clocks: Open the lab on 12 and 24 hour clock and drag the time round a full day.
- Time intervals: Count on from the start time in friendly steps: first to the next whole hour, then whole hours, then the remaining minutes.
- Timetables and time zones: A timetable lists each journey in a column and each stop in a row.
- 24-hour clock: four digits; add 12 for p.m. times after 1 p.m.
- Intervals: count on to the next hour, then whole hours, then minutes.
- Decimal hours: decimal part × 60 gives minutes.
- Timetables: read down one column for one journey.
- Time zones: 'ahead' means add the difference; 'behind' means subtract.
One picture every idea returns to
To find the time between two times, count on: to the next whole hour, then whole hours, then the minutes left. Never subtract times like ordinary decimals, because an hour has 60 minutes, not 100.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Sixty, not a hundred.. Time counts in 60s and 24s, not in 10s. | Whole class, then pairs |
| 5 to 13 min | Teach and check: 12-hour and 24-hour clocks | Open the lab on 12 and 24 hour clock and drag the time round a full day. Project tab 5 of the lab (Ratio, rates and percentages lab, time) and let a student drive it while the class predicts. Model the worked example Converting units of time on the board, one line at a time. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Time intervals | Count on from the start time in friendly steps: first to the next whole hour, then whole hours, then the remaining minutes. Model the worked example Count on on the board, one line at a time. Your turn: How many minutes are there from 10 45 to 14 10? | Pairs |
| 21 to 30 min | Teach and check: Timetables and time zones | A timetable lists each journey in a column and each stop in a row. Model the worked example Reading a timetable on the board, one line at a time. | Frayer Model |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 13 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Timetables and time zones, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Frayer Model
Pairs fill a four-box grid for the key term: definition, characteristics, examples and non-examples. The non-examples box is where the misconceptions surface, so give it the most time.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| 12.40 a.m. is just after MIDNIGHT, so it is 00 40, not 12 40. | And 57.6 hours is 57 hours 36 minutes, not 57 hours 60 minutes. |
| Do not subtract times as decimals: \(13.22 - 8.47 = 4.75\), which is NOT 4 h 75 min or 4.75 hours. | The correct interval is 4 h 35 min. |
| 'Ahead' means the clock shows a LATER time. | When you fly to a place that is ahead, add the time difference to the arrival time in your home time; do not subtract it. |
Time: 12- and 24-hour clock, time calculations: worksheet
6 questions, 13 marks. Written in the style of the papers; no past paper question is reproduced.
(a) Write 7.05 p.m. in the 24-hour clock. (b) Write 00 25 in the 12-hour clock.
How many seconds are there in one day?
A film starts at 18 50 and lasts 2 hours 25 minutes. At what time does it finish? Give your answer in the 12-hour clock.
Write 2.4 days in hours and minutes.
Part of a bus timetable is shown.
| Stop | Bus A | Bus B | Bus C |
|---|---|---|---|
| Station | 06 50 | 07 35 | 08 20 |
| Market | 07 06 | 07 51 | 08 36 |
| Hospital | 07 23 | 08 08 | 08 53 |
| Airport | 07 58 | 08 43 | 09 28 |
(a) How long does Bus A take from the Station to the Airport?
(b) Pia arrives at the Hospital stop at 07 30. She takes the next bus to the Airport. How long after arriving at the Hospital stop does she reach the Airport?
A plane leaves Sydney at 10 45 local time on Monday. It lands in Los Angeles at 06 15 local time on the same Monday. Los Angeles time is 18 hours behind Sydney time.
Calculate the flight time.
Answer key and marking notes
- (a) 19 05
- (b) 12.25 a.m.
\(24 \times 60 \times 60 = 86\,400\) seconds
- 18 50 + 2 h = 20 50; 20 50 + 25 min = 21 15.
- 21 15 is 9.15 p.m.
- \(2.4 \times 24 = 57.6\) hours.
- \(0.6 \times 60 = 36\) minutes, so 57 hours 36 minutes.
- (a) 06 50 to 07 58 is 1 hour 8 minutes.
- (b) The next bus from the Hospital is Bus B at 08 08, reaching the Airport at 08 43.
- 07 30 to 08 43 is 1 hour 13 minutes.
- Change the landing time to Sydney time: 06 15 Monday + 18 h = 00 15 Tuesday.
- 10 45 Monday to 00 15 Tuesday: 10 45 to 24 00 is 13 h 15 min, plus 15 min.
- Flight time = 13 hours 30 minutes.
6 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Write 12.25 a.m. as a time on the 24-hour clock.
- A00 25
- B12 25
- C24 25
- D01 25
A coach leaves at 09 38 and arrives at 14 17 on the same day. How long is the journey?
- A4 h 39 min
- B4 h 79 min
- C5 h 21 min
- D4 h 21 min
A night bus leaves at 21 35 and arrives at 05 10 the next morning. How long is the journey?
- A7 h 35 min
- B16 h 25 min
- C8 h 25 min
- D7 h 25 min
Write 3.6 days in hours and minutes.
- A86 h 24 min
- B86 h 40 min
- C86 h 4 min
- D78 h
A flight leaves Tokyo at 10 15 local time and takes 12 hours 40 minutes to reach London. London time is 9 hours behind Tokyo time. What is the local time in London when the flight lands?
- A13 55
- B07 55 the next day
- C22 55
- D12 55
Buses leave a station at 06 40 and then every 35 minutes. The journey to the airport takes 52 minutes. Maya arrives at the station at 09 05 and takes the next bus. At what time does she reach the airport?
- A10 27
- B09 52
- C10 02
- D09 57
Quiz key
a.m. times run from midnight to midday, so 12.25 a.m. is 25 minutes after midnight: 00 25. The tempting 12 25 is 12.25 p.m., just after MIDDAY. 24 25 is not a valid 24-hour time, because the clock goes back to 00 00 at midnight.
09 38 to 10 00 is 22 min; 10 00 to 14 00 is 4 h; 14 00 to 14 17 is 17 min. Total \(= 4\) h \(22 + 17 = 39\) min. The tempting 4 h 79 min subtracts the times as decimals (\(14.17 - 9.38 = 4.79\)), forgetting there are only 60 minutes in an hour. 5 h 21 min subtracts the hours and minutes separately the wrong way round.
21 35 to midnight is 2 h 25 min; midnight to 05 10 is 5 h 10 min. Total \(= 7\) h 35 min. The tempting 16 h 25 min subtracts 05 10 from 21 35, which is the time from 05 10 to 21 35 on the same day, not the overnight journey.
\(3.6 \times 24 = 86.4\) hours, and \(0.4 \times 60 = 24\) minutes, so 86 h 24 min. The tempting 86 h 40 min reads the decimal 0.4 as 40 minutes. 86 h 4 min is the same misreading, and 78 h treats 3.6 days as 3 days 6 hours.
London is 9 hours behind, so the plane leaves at \(10\ 15 - 9\) h \(= 01\ 15\) London time. Adding 12 h 40 min gives 13 55. The tempting 07 55 the next day ADDS the 9 hours, but 'behind' means London clocks show an earlier time. 22 55 ignores the time difference altogether.
Departures: 06 40, 07 15, 07 50, 08 25, 09 00, 09 35. The 09 00 bus has already gone, so she takes the 09 35, arriving at \(09\ 35 + 52\) min \(= 10\ 27\). The tempting 09 52 uses the 09 00 bus, which left before she arrived. 10 02 counts the buses every 30 minutes, and 09 57 adds 52 minutes to her arrival time with no wait.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.