Year 5 Mathematics — Australian Curriculum v9 [AC9M5T03]
Welcome, class! Today we will practise turning 12-hour times into 24-hour times, and master the Timeline Jump Strategy to find the time difference between morning and afternoon events.
This sequence supports content descriptor AC9M5T03.
Reinforce that 24-hour time does not use a.m./p.m. or colons.
Remind students of the midnight exception: 12:00 a.m. becomes 0000. 12:30 a.m. becomes 0030.
Correct! It is a morning time (a.m.), so the hours remain under 12. We write 4 digits with no colon: 0715.
Invite a student up to tap the correct button. Highlight that a leading zero is required for single digit hours in 24-hour time.
Correct! Since 15 is 13 or greater, subtract 12 from 15 to get 3, and add p.m. because it is after noon. The time is **3:30 p.m.**
Help students see the subtraction step: 15 − 12 = 3. Reinforce that a.m./p.m. is vital in 12-hour format.
Correct! It is p.m. (afternoon/night), so we add 12 to the hours: 8 + 12 = 20. The 24-hour time is **2045**.
Have students practice saying "twenty forty-five hours" and explain that adding 12 marks PM times.
Correct! 0910 has a leading zero, indicating morning (a.m.). The 12-hour time is **9:10 a.m.**
Ensure students understand that times starting with numbers less than 12 are morning a.m. times (except the midnight 00 hour).
Correct! The midnight hour (12:00 a.m. to 12:59 a.m.) converts to **00** in 24-hour time. So the answer is **0020**.
Emphasise this slide! Midnight is a notorious confusion point. Explain that 0000 is 12:00 a.m. on the dot. Therefore, 12:20 a.m. is 20 minutes past midnight, or 0020.
Correct! 23 is greater than 12, so it is p.m. Subtract 12 from 23 to get 11. The time is **11:15 p.m.**
Confirm that students understand this final review step before diving into Section 2 (elapsed calculations).
Demonstrate the step-by-step calculator. Point out how drawing timeline jumps makes bridging noon simple.
Step 1 secures the whole hour (10:00 a.m.), Step 2 bridges full hours across 12:00, and Step 3 adds the remaining target minutes.
Invite a student up to activate the steps. Highlight that jumping from 9:00 a.m. to 4:00 p.m. crosses noon.
Encourage them to think: 9 to 12 is 3 hours, then 12 to 4 is 4 hours. 3 + 4 = 7 hours.
In this question, the minutes (45 min + 50 min) sum up to 95 minutes.
Show students how to convert this: 95 mins = 1 hour 35 mins. Adding 1 hour to 6 hours gives the final answer of 7 hours 35 minutes.
Correct!
1. Jump 1 (minutes): 7:40 a.m. → 8:00 a.m. = **20 min**
2. Jump 2 (hours): 8:00 a.m. → 3:00 p.m. = **7 hours**
3. Jump 3 (minutes): 3:00 p.m. → 3:10 p.m. = **10 min**
Total = 7 h + 20 min + 10 min = **7 hours 30 minutes**!
Have students sketch their three arrows on their handouts before validating with this quiz slide.
Correct!
1. Jump 1: 11:20 a.m. → 12:00 noon = **40 min**
2. Jump 2: 12:00 noon → 6:00 p.m. = **6 hours**
3. Jump 3: 6:00 p.m. → 6:45 p.m. = **45 min**
Total = 6 h + 85 min = **7 hours 25 minutes**!
Remind students: 85 minutes is 1 hour and 25 minutes. Therefore, 6 hours + 1 hour 25 mins = 7 hours 25 mins.
Correct!
1. Jump 1: 6:15 a.m. → 7:00 a.m. = **45 min**
2. Jump 2: 7:00 a.m. → 12:00 noon = **5 hours**
3. Jump 3: 12:00 noon → 12:50 p.m. = **50 min**
Total = 5 h + 95 min = **6 hours 35 minutes**!
Solidify understanding of the 12-hour jumps before transitioning to Section 3 which uses 24-hour times.
Explain that 24-hour values work exactly the same way. The 4 digits can be treated just like normal times.
0940 represents 9:40 a.m. 1420 represents 2:20 p.m. The step-by-step calculator makes the visual transition clear.
In this problem, minutes sum to 90 (45 + 45). Show students how this carries over into 1 hour and 30 minutes.
Adding that to the 7 hours yields 8 hours 30 mins.
This is the final step-by-step calculator slide. Encourage students to solve the next three multiple choice questions on their mini-whiteboards using the same three jumps.
Correct!
1. Jump 1: 0850 → 0900 = **10 min**
2. Jump 2: 0900 → 1600 = **7 hours**
3. Jump 3: 1600 → 1610 = **10 min**
Total = 7 h + 10 min + 10 min = **7 hours 20 minutes**!
Have students practice converting the starting and ending times to 12-hour first to see if they get the same answer (8:50 a.m. to 4:10 p.m. = 7h 20m).
Correct!
1. Jump 1: 1115 → 1200 = **45 min**
2. Jump 2: 1200 → 1800 = **6 hours**
3. Jump 3: 1800 → 1845 = **45 min**
Total = 6 h + 90 min = **7 hours 30 minutes**!
Ensure they carry the 90 minutes correctly: 90 mins = 1 hour 30 mins. 6 hours + 1 hour 30 mins = 7 hours 30 mins.
Correct!
1. Jump 1: 0530 → 0600 = **30 min**
2. Jump 2: 0600 → 1300 = **7 hours**
3. Jump 3: 1300 → 1310 = **10 min**
Total = 7 h + 30 min + 10 min = **7 hours 40 minutes**!
Congratulate the students on completing all elapsed calculations. Now proceed to the summary and exit assessment description.
Time to test your skills individually!
Please open your tablets or computers and load the **Microsoft Forms Assessment: Lesson 14 Time calculations** to complete the final 10 questions.
Ensure all students have accessed the Microsoft Forms document path and are working independently.
Review standard results formatively to identify if any students require additional timeline scaffolding.
Select a slide to see accompanying pedagogical notes and teaching tips.