Year 4 Mathematics · AC9M4M03

Duration, am/pm and time conversions

Solve problems involving duration, situations using am and pm, and conversions between units of time

Ready to project and teach

Learning goalsSay it simply

Duration is the amount of time that passes. Count elapsed intervals between a known start and finish, keeping the day and am/pm label. Break a journey at a whole hour, noon or midnight and use 60 minutes per hour and 60 seconds per minute.

Learning intention: Solve duration problems, explain am/pm and day changes, convert time units, create timetables and explore named public First Nations accounts of repeated sky patterns.

Find a duration, starting time or finishing time and state the day and am/pm where needed.
Label a timeline through noon or midnight and add the elapsed jumps.
Convert between hours, minutes and seconds, including mixed units.
Create a timetable with activity and rest durations and check its total.
Explain how a repeating sky pattern in an attributed public account can mark passing time.

Learning routine: Identify what is missing → record days and am/pm → draw or count useful jumps → convert units → check the result in context.

Clean visual examplesOne-page board

Clean one-page examples

AC9M4M03 — worked mathematical models

Example 1

Find duration from 9:35 am to 1:10 pm on Monday

Point on the timeline	Elapsed jump
9:35 am Monday	Start
10:00 am Monday	25 minutes
1:00 pm Monday	3 hours
1:10 pm Monday	10 minutes

Worked total: 25 min + 3 h + 10 min = 3 h 35 min = 215 min. The 3-hour jump crosses noon. The day stays Monday and the clock label changes from am to pm.

Teacher asks: “Why is this not 1:10 minus 9:35 as ordinary digits?” Expected response: an hour contains 60 minutes and the journey crosses noon. Point to each elapsed interval if students subtract only the minute digits.

Example 2

Cross midnight with the day visible

Midnight here is 12:00 am at the start of Saturday.

From 10:50 pm Friday to midnight is 1 h 10 min. From midnight to 12:35 am Saturday is 35 min. Total 1 h 45 min = 105 min. The same clock label on a different day could mean a different interval, so include the days.

Quick checkpoint: “What day is it 10 minutes after 11:55 pm Tuesday?” Answer: 12:05 am Wednesday. Continue when both label and day are correct; otherwise mark midnight and count 5 minutes on each side.

Example 3

Find an unknown start or finish

Finish: 11:50 am Wednesday + 35 min. Use 10 min to noon, then 25 min: 12:25 pm Wednesday. Start: an event ending 12:20 am Tuesday after 50 min started 11:30 pm Monday; go back 20 min to midnight then 30 min to Monday evening. Check by counting forward 50 min.

Backward counting locates the start in the previous evening.

Example 4

Convert and compare durations

Duration	Worked conversion
2 h 15 min	2 × 60 + 15 = 135 min
150 min	120 + 30 min = 2 h 30 min
1 day 6 h	24 + 6 = 30 h
90 s	60 + 30 s = 1 min 30 s
2 min 20 s	2 × 60 + 20 = 140 s

Use 60 minutes per hour, 60 seconds per minute and 24 hours per day. For 145 min versus 2 h 20 min, convert the second duration to 140 min; 145 min is 5 min longer. Clock time 12:30 pm and duration 12 h 30 min have different meanings.

Example 5

Read and plan a timetable

Every finish becomes the next start; the rest is part of the total.

Relay 30 min + break 15 min + long jump 40 min = 85 min = 1 h 25 min. The start 10:20 am plus 1 h 25 min reaches 11:45 am. When choosing travel, first check the arrival deadline, then departure and transfer time.

Curriculum examplesCopied content

Content description: solve problems involving the duration of time including situations involving “am” and “pm” and conversions between units of time

Elaboration 1

E1: calculating the amount of time between 2 events, such as the start and finish of a movie, a bus journey or a flight, including cases where the starting and finishing times are written using “am” and “pm” notation

Worked progression: On Friday, 11:45 am to 12:25 pm is 15 min to noon plus 25 min = 40 min. For 10:50 pm Friday to 12:35 am Saturday, split at midnight to obtain 1 h 45 min. Students draw both timelines, label each jump and name the days. For journeys or flights, use times in the same stated local time; time-zone conversion is outside this lesson.

Elaboration 2

E2: converting units of time using relationships between units, such as 60 minutes in an hour and 60 seconds in a minute, to solve problems; for example, creating a daily timetable for an activity such as an athletics carnival or planning an exercise routine with activities and rests

Convert and create: 2 h 15 min = 135 min; 90 s = 1 min 30 s. Create a Wednesday timetable starting 10:45 am with a 20-minute warm-up, 35-minute relay, 10-minute rest and 25-minute long jump. Worked answer: 10:45–11:05 am; 11:05–11:40 am; 11:40–11:50 am; 11:50 am–12:15 pm. Total 20 + 35 + 10 + 25 = 90 min = 1 h 30 min. Require all start/finish labels and the calculation including the rest.

Elaboration 3

E3: exploring First Nations Australians’ explanations of the passing of time through cultural accounts about cyclic phenomena involving sun, moon and stars

ACARA’s public background names Nyangumarta use of the Sun for days and Moon phases for months. Read the ACARA account.

In the National Museum’s Sky stories, Wiradjuri astrophysicist Kirsten Banks links the Emu’s position with egg-gathering season. Read the named speaker’s public account.

Pattern to discuss	How repetition can mark time
Daily light and darkness	Dawn, day, dusk and night return in a daily cycle.
Changing Moon phases	A similar phase returns after a lunar cycle; do not assume every calendar month has exactly that duration.
A seasonal sky pattern	A recurring position can help identify a time of year in the supplied account.

Teacher asks: “What returns, and what interval can that return help identify?” Students label an observable cycle in words and give the People or speaker and source. The cultural accounts are specific, publicly attributed examples; do not present them as one calendar for all First Nations communities. Learn from authorised local voices when extending the discussion, and follow local protocols. Students explain the supplied observations; they are not asked to invent a cultural story or copy cultural artwork.

Expected reasoning: A returning pattern provides a marker for passing time. A bus journey’s exact minutes still require start/end clock readings or a timer; a seasonal indicator alone cannot provide those minutes.

Questions and answersWith answers

How long is 9:35 am to 1:10 pm on Monday?

Answer: 3 h 35 min. Count 25 min to 10:00, 3 h to 1:00 pm and 10 min to 1:10 pm.

How many minutes are 2 h 15 min?

Answer: 2 × 60 + 15 = 135 minutes.

How long is 10:50 pm Friday to 12:35 am Saturday?

Answer: 1 h 45 min = 105 min. Split at midnight, the start of Saturday.

What do 12 pm and 12 am mean?

Answer: 12:00 pm is noon. 12:00 am is midnight at the start of the named day; use the day when a problem crosses midnight.

Which is longer: 145 min or 2 h 20 min?

Answer: 145 min is 5 min longer because 2 h 20 min = 140 min.

How can repeated sky patterns help mark time?

Answer: A returning pattern marks another cycle. Name the particular People or public speaker/source when discussing the account; do not assume identical traditions across communities.

Practice and reviewReady for practice

1. Timeline jumps

On Tuesday, find 2:48 pm to 5:27 pm. Worked answer: 12 min to 3:00 pm, 2 h to 5:00 pm, 27 min to 5:27 pm. Total 2 h 39 min = 159 min. Students draw the jumps and check that their sum connects the given times.

2. Schedule comparison

Event, all Wednesday	Start	Finish	Duration
Lesson	9:10 am	10:25 am	1 h 15 min = 75 min
Trip, same local time	11:45 am	2:05 pm	2 h 20 min = 140 min

The trip is 65 min longer: 140 − 75 = 65 min = 1 h 5 min. Students explain why the units must match before comparing.

3. Midnight crossing

Draw the overnight timeline for 10:50 pm Friday to 12:35 am Saturday. Label midnight as the start of Saturday. Answer: 1 h 10 min + 35 min = 1 h 45 min = 105 min. Ask which day contains each part of the journey.

4. Create a short exercise routine

Plan three 40-second activities with two 20-second rests between them. Write names, sequence and duration calculation. One named sequence: marching 40 s, rest 20 s, arm circles 40 s, rest 20 s, balancing 40 s. Total: 3 × 40 + 2 × 20 = 160 s = 2 min 40 s. Starting 9:00 am, the finish is 9:02:40 am. A rest is not added after the final activity.

Assessment-style questions and review hints

A show on Tuesday starts 11:40 am and ends 12:15 pm. Find its duration.

Answer: 20 min to noon + 15 min = 35 min. Review hint: noon changes am to pm.

A routine lasts 185 seconds. Express it in minutes and seconds.

Answer: 3 min 5 s because 3 × 60 = 180 and 5 s remain. Review hint: group by 60, not 100.

A journey ends 12:30 am Friday and takes 50 min. Find the start.

Answer: 11:40 pm Thursday. Back 30 min to midnight, then 20 min into Thursday. Review hint: count backwards across the day boundary.

Common misconceptions

Subtracting only clock digits: 10:55 am to 11:10 am is 5 + 10 = 15 minutes, not 10 − 55.
Reversing 12 am and 12 pm: label noon 12:00 pm and midnight 12:00 am.
Treating minutes as hundredths: 1 h 40 min = 60 + 40 = 100 minutes.
Omitting the day: a crossing from pm to am must state the same/next-day relationship. Use midnight as a clear boundary.
Dropping rests or gaps: total programme time includes specified breaks.
Generalising a cultural account: keep the named People or speaker and source; a public example does not establish one calendar shared by all communities.

Support / Core / Extend

Support: Use a teaching clock and timelines within one hour, then across one hour. Label the known start and finish; place counters for 10- and 5-minute jumps.
Core: Find start/end/duration through noon or midnight, use hour-minute-second conversions, create a complete timetable and explain a sourced cyclic-time account.
Extend: Compare two routes in the same local time including a transfer: a 40-minute journey + 15-minute wait + 25-minute journey totals 80 min; compare it with a direct 85-minute journey. The connection is 5 min faster if the given timings hold.

Exit ticket and mastery evidence

Exit ticket: (1) Draw and label each jump from 11:50 am to 12:35 pm on Monday. (2) Convert 2 min 45 s to seconds. (3) Find the end of a 30-minute activity starting 11:45 pm Tuesday. (4) Explain what makes an observed pattern cyclic and identify a People or public speaker/source from E3.

Answers and evidence: (1) 10 min to noon + 35 min = 45 min, with Monday and am/pm labels. (2) 120 + 45 = 165 s. (3) 12:15 am Wednesday. (4) A cycle returns through a repeating pattern; for example identify Nyangumarta in the cited ACARA account or Kirsten Banks, Wiradjuri, in NMA’s Sky stories. Require the return idea plus attribution. Revisit 60-unit grouping if conversion is wrong; mark midnight and the day name if (3) is wrong; revisit the supplied source if attribution is missing.

Curriculum alignmentStart here

AC9M4M03: solve problems involving the duration of time including situations involving “am” and “pm” and conversions between units of time

Prerequisites: Read hours/minutes on familiar clocks and count in fives. Must teach: duration, am/pm, conversions, timetables and the cyclic-time elaboration. Boundary: Keep problems in the same stated local time. Formal time zones, daylight-saving changes and 24-hour notation conversion are not required targets; the core uses 12-hour labels with explicit days.

Australian Curriculum Version 9.0 mathematics resources (QCAA)

Teach & ExplainTeaching slides and samples

Teach this topic step by step

Explore optional teaching slide packs for classroom lessons and explanations at home.

Browse Teach & Explain · Browse Print & Go

Teachers: follow SkillrHub on TPT, then email us to request a free sample before buying. Include the year, subject and topic or curriculum code.

Request a free sample

After trying the sample, honest feedback is welcome. A TPT review is optional, where available, and does not need to be positive.