Mathematics classroom notes
Year 4 - Time — using am and pm
Strand / topic: Measurement and Geometry / Time — using am and pm
Based on Pi Leo Academy's Victorian Curriculum F-10 Mathematics year-level guide and aligned to NAPLAN-style mathematical reasoning. Official curriculum code: Not stated in the provided curriculum source.
By the end of this note, students should be able to explain time — using am and pm, use a clear method, solve simple and test-style questions, and check their answers for Year 4 Measurement and Geometry work.
It helps students read timetables, plan routines, arrive on time and compare durations. This topic builds the reasoning, fluency and confidence students need for future NAPLAN-style questions and everyday mathematics.
How do we measure time?
Time is counted in seconds, minutes, hours, days and weeks.
From 3:10 pm to 3:40 pm is a 30-minute jump.
For Year 4, focus on understanding the idea before rushing to the final answer.
Think about it: school bells, sport training and bus timetables all use time.
Use this visual to organise time — using am and pm before calculating.
Jump to the next friendly time before adding the rest.
What you need to know for this topic
Use this as a study checklist before trying quizzes, worksheets or NAPLAN-style questions.
Time language
- am and pm
- seconds, minutes, hours, days and weeks
- 12-hour and 24-hour time
- start time, finish time and duration
Time calculations
- convert time units
- add and subtract mixed time units
- find elapsed time
- read timetables and schedules
Careful thinking
- remember 60 minutes in an hour
- use timeline jumps
- check if the time crosses midday or midnight
1 What this means
Time maths helps us read clocks, calendars and timetables. Start by learning to mark the start and finish, then count elapsed time in manageable jumps. A helpful visual is a clock face, timeline or timetable. For example, this idea can be used when planning a trip or comparing two event times.
Time uses groups of 60, so students need timelines rather than ordinary base-ten counting. In Year 4, students should first ask, 'What is the question really asking me to find?' Then they can draw a picture, make a table, use a number line, write a formula or build an equation. The final answer should match the story, the units and the size of the numbers.
- Use a timeline because time is grouped in 60 minutes, not 100.
- Break long durations into friendly jumps such as 15 minutes, 30 minutes or 1 hour.
- Watch for am, pm, midnight, midday and 24-hour time.
- Write the final answer with sensible units such as minutes, hours or days.
2 Important rules / ideas
There are 60 seconds in a minute and 60 minutes in an hour.
Use jumps to the next hour, then add the remaining minutes.
Check whether the event is before or after midday.
Important vocabulary
How long something lasts.
The time between a start and finish.
A table showing times for events or travel.
Time written from 00:00 to 23:59.
3 Step-by-step method
- Find the start and finish times.
- Break the time into friendly jumps.
- Add the jumps to find duration or arrival time.
- Check am, pm or 24-hour notation.
4 Worked examples
What time is 30 minutes after 2:15 pm?
- Add 30 minutes to 2:15 pm.
- 2:45 pm.
A movie starts at 6:40 pm and ends at 8:05 pm. How long is it?
- 6:40 to 7:40 is 1 hour.
- 7:40 to 8:05 is 25 minutes.
- Total = 1 hour 25 minutes.
Write 9:30 pm in 24-hour time.
- For pm times after noon, add 12 to the hour.
- 9 + 12 = 21.
- 9:30 pm = 21:30.
Training starts at 4:15 pm and lasts 75 minutes. When does it finish?
- 75 minutes = 1 hour 15 minutes.
- 4:15 pm + 1 hour = 5:15 pm.
- Add 15 minutes: 5:30 pm.
5 More examples
From 8:50 am to 9:25 am.
Jump 10 minutes to 9:00, then 25 minutes to 9:25. Total 35 minutes.
Write 4:15 pm in 24-hour time.
Add 12 to the hour: 16:15.
NAPLAN-style thinking
In NAPLAN-style questions, time — using am and pm may appear as a short calculation, a word problem, a diagram, a table or a multi-step reasoning question. Students should slow down and decide what the question is really asking before calculating.
Estimate first and eliminate answers that are too small, too large or use the wrong unit.
Write only the answer required, but use working on paper to avoid mental slips.
Circle the numbers, underline the action words and decide whether all numbers are needed.
Do one step at a time and label intermediate answers so the final step is clear.
6 Common mistakes
There are 60 minutes in an hour, not 100.
Check whether the time crosses midday or midnight.
Use jumps along a timeline.
- Choosing the first operation seen in the wording.
- Forgetting units, labels or place value.
- Stopping after the first step when the question asks for a final comparison.
7 Tips to remember
Never treat 1 hour as 100 minutes.
Timeline jumps are clearer than trying to subtract time vertically.
Write hours and minutes so the answer cannot be misread.
Parent teaching tips
- Ask your child to explain the method aloud before writing the answer.
- Use a real-life context at home, such as shopping, cooking, sport scores, maps or timetables.
- Praise clear working and checking, not only speed.
- Encourage a quick diagram or table for word problems before calculating.
Remember
Time uses 60 minutes in an hour.
8 Quick practice
- What time is 30 minutes after 2:15 pm?
- A movie starts at 6:40 pm and ends at 8:05 pm. How long is it?
- Write 9:30 pm in 24-hour time.
- Training starts at 4:15 pm and lasts 75 minutes. When does it finish?
9 Answers / explanation
Question 1
Answer: 2:45 pm.
Add 30 minutes to 2:15 pm. 2:45 pm.
Question 2
Answer: Total = 1 hour 25 minutes.
6:40 to 7:40 is 1 hour. 7:40 to 8:05 is 25 minutes. Total = 1 hour 25 minutes.
Question 3
Answer: 9:30 pm = 21:30.
For pm times after noon, add 12 to the hour. 9 + 12 = 21. 9:30 pm = 21:30.
Question 4
Answer: Add 15 minutes: 5:30 pm.
75 minutes = 1 hour 15 minutes. 4:15 pm + 1 hour = 5:15 pm. Add 15 minutes: 5:30 pm.
Extension challenge
Create your own multi-step question for this topic using an Australian context, then solve it and explain each step.
Hint: Use shopping, sport, maps, timetables, weather, school events or measurement at home.
Answer guide
Answers will vary. A strong answer includes clear working, correct units and a final sentence.
Quick revision
- Know what time — using am and pm is asking you to find.
- Choose a diagram, table, formula, number line or equation before calculating.
- Show enough working that you can find and fix mistakes.
- Check the final answer, units and reasonableness.