Elapsed Time Across Hours and Days

Warning: Your screen size is quite small for viewing this. Rotate your device into landscape mode if you can.

1 Getting Started
2 Watch and Notice
3 Try It Together
4 Sketch the Bridging Line in Your Copy
5 Class Challenge
6 What Did We Notice?
7 What's Next
Pupil practice

1 - Getting Started ~4 mins

Illustration for Getting Started A film starts at 19:40 and ends at 22:15. How long is the film?

Some people try to just subtract the digits and get muddled when the minutes seem to go backwards. Before we work it out together, have a think: why can't we simply subtract 19:40 from 22:15 the way we subtract ordinary numbers? It is completely fine not to know yet, we will figure this out together in a moment.

Teacher Notes

Display the two times side by side and take three hands-up answers, not open call-outs. Give five seconds of quiet think-time first.

Listen for the trap: a pupil who says '22 take 19 is 3, 15 take 40 is...' has hit the borrowing problem that makes counting-up the better method. Do not resolve it yet, that is the job of the next step. Just surface the puzzle.

👇 Mark your steps as done as you complete them.

+5 XP

2 - Watch and Notice ~11 mins

19:40 to 22:15

Watch the two clocks and the hops drawn beneath them. We count up in three hops: 20 minutes to reach 20:00, then 2 whole hours to 22:00, then 15 minutes on to 22:15. Add the hops: 20 min + 2 h + 15 min = 2 h 35 min.

08:55 to 13:10

This time the hops are: 5 minutes to 09:00, then 4 whole hours to 13:00, then 10 minutes on to 13:10. What total do the hops give us?

22:30 to 06:15 next morning

This finish time is the next morning, so the hops land on midnight first. Watch how they stop at 00:00, then carry on into the new day. The duration keeps adding forward right across midnight.

09:00 Monday to 14:00 Wednesday

This journey is longer than a single day, so the clock face cannot hold it all. We count it on paper instead. Monday to Tuesday is one whole day, which is 24 hours. Tuesday to Wednesday is another whole day, another 24 hours. That is 24 + 24 = 48 hours so far, landing us at 09:00 on Wednesday. From 09:00 to 14:00 on Wednesday is 5 more hours. So the whole span is 48 + 5 = 53 hours.

14:20 to 17:05, setting the arrival

Now watch the other way round. A train leaves at 14:20 and the journey takes 2 h 45 min. We count that duration up onto the clock to find the arrival: 40 min to 15:00, then 2 hours to 17:00, then 5 minutes on to 17:05. So the train arrives at 17:05. Same hops, but this time we add the duration to a start time to land on the finish.

Teacher Notes

Walk each example aloud, one at a time, naming each hop from the board text as you go.

19:40 to 22:15 — emphasise the order of the three hops: to the next whole hour first, then the whole hours, then the last minutes. Say 'never subtract the digits, count up'.
08:55 to 13:10 — pause before the total and ask the class to call out 4 h 15 min; revoice it as '5 min plus 4 hours plus 10 min'.
22:30 to 06:15 — point at the highlighted 00:00 hop and say 'we always stop at midnight first, then carry on into the new day'. The total is 7 h 45 min.
09:00 Monday to 14:00 Wednesday — this one is worked on the board text, not the clock. Walk pupils through the two whole days as 24 + 24 = 48 hours, then the 5 extra hours = 53 hours. Stress that days go on paper, not the clock face. Leave this working on the board so it can be referred back to later.
14:20 to 17:05, setting the arrival — this is the forward move pupils will need in the Class Challenge: start time plus a given duration to find the arrival. Count the 2 h 45 min up onto the clock and land on 17:05. Say 'same hops, but now we add the duration to the start to find where we land'.

👇 Mark your steps as done as you complete them.

+10 XP

3 - Try It Together ~7 mins

Today we work through a fresh journey together: a train leaves at 14:20 and the journey takes 2 h 45 min. Before we touch the clock, let's predict each hop aloud: first the jump to the next whole hour, then the whole hours, then the last minutes. Then a pupil sets the arrival on the clock and we press Check to see if the hands are right and the hops match what we predicted.

Teacher Notes

This round is for talking it through together. A pupil comes to the board, but the class predicts first and the answer stays hidden until Check is pressed.

Before anyone touches the hands, ask one pupil to predict the first hop (40 min to 15:00), a second to predict the whole hours (2 hours to 17:00), a third to predict the last minutes (5 min to 17:05). Then the pupil at the board sets the arrival hands to 17:05 and presses Check; the class confirms the revealed hops match the predictions. Total 2 h 45 min.

Watch for the pupil who tries to do 17 − 14 = 3 and stalls on the minutes — revoice the counting-up route as the reliable one.

+15 XP

4 - Sketch the Bridging Line in Your Copy ~3 mins

COPYBOOK MOMENT

Illustration for Sketch the Bridging Line in Your Copy In your maths copy, for each elapsed-time example draw a short bridging number line. Mark the start time, then write each hop you counted along it (for example: 20 min, then 2 h, then 15 min). Record the total beside it.

Do this for these three journeys:

19:40 to 22:15
08:55 to 13:10
14:20 to 17:05

Teacher Notes

Walk the room glancing for the order of the hops, to the next whole hour first, then whole hours, then the last minutes. This is whole-class copybook practice, not marking. A pupil who has skipped the hop to the next whole hour is the one to catch.

+10 XP

5 - Class Challenge ~8 mins

Today we work through these journeys: each one gives a start time and how long the journey takes, and you set the arrival clock by counting the duration up onto the hands, just like the train example we set together. The elapsed readout will confirm the duration once you've set the hands.

Watch out

The last one crosses midnight, so remember to stop at 00:00 first.

Set the arrival time

Teacher Notes

These are the practice questions. Pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

For each item, the pupil counts up the given duration from the start time and moves the hands to the arrival, exactly as modelled with the 14:20 train; the elapsed readout confirms the journey length. The class predicts the arrival aloud before the pupil sets the hands.

The last item crosses midnight. Pause here and ask the class to count to 00:00 first (1 h 20 min), then on into the new day (6 h 25 min). Revoice: 'stop at midnight, then carry on'. The two-day duration is not on the clock today; if a fast finisher asks, point them back to the board working of 09:00 Mon to 14:00 Wed = 53 hours that is still up on the board.

+15 XP

6 - What Did We Notice? ~2 mins

MATHS TALK

One pupil says you can always just subtract the start time from the finish time to find how long a journey is. Another says you have to count up in hops. Who is right, and how would you settle the argument?

Teacher Notes

Listen for pupils naming the borrowing problem as the reason subtracting the digits goes wrong (the minutes seem to go backwards). Revoice a strong answer as 'counting up never makes you borrow, so it never trips you up'.

Steer them to a settling test: try both methods on 19:40 to 22:15 and see which gives 2 h 35 min cleanly. Head off the misconception that the landing time is the same as the duration when you cross midnight.

+10 XP

7 - What's Next ~3 mins

What we learned today

To find elapsed time, count up in hops: to the next whole hour, then the whole hours, then the last minutes.
You can also count a duration up from a start time to set the arrival on the clock.
When a finish time is the next day, count up to midnight (00:00) first, then carry on into the new day.
For spans longer than a day, count each whole day as 24 hours and add the extra hours on paper, like 09:00 Monday to 14:00 Wednesday = 53 hours.

Coming up

Next we read real timetables and schedules, and we start to think about time zones, what time it is in New York or Sydney when it is afternoon here in Ireland.

Teacher Notes

Keep this brisk. Recap the three hops once more and the midnight waypoint before moving on.

+5 XP

Pupil practice

Module 6 · Time and Money Shape & Space

Lesson 61 · Elapsed Time Across Hours and Days

Download Activity Book page (PDF)

End of lesson

123learn · Online learning platform

Unlock the full learning experience

You're previewing this lesson. Get full access to this lesson and hundreds more — each one ready to teach, with interactive activities, printable resources and pupil progress tracking built in.

Hundreds of curriculum-aligned lessons

Interactive activities in every lesson

Printable resources & progress tracking

Get started

Copyright Notice
This lesson is copyright of Coding Ireland 2017 - 2025. Unauthorised use, copying or distribution is not allowed.

Teacher Class Feed

1 - Getting Started ~4 mins

2 - Watch and Notice ~11 mins

19:40 to 22:15

08:55 to 13:10

22:30 to 06:15 next morning

09:00 Monday to 14:00 Wednesday

14:20 to 17:05, setting the arrival

3 - Try It Together ~7 mins

4 - Sketch the Bridging Line in Your Copy ~3 mins

5 - Class Challenge ~8 mins

Set the arrival time

6 - What Did We Notice? ~2 mins

7 - What's Next ~3 mins

What we learned today

Coming up

Unlock the full learning experience

XP