Hop to the hour: time and timetables
The Short Answer
Time is the one measure that does not work in tens, so subtracting one clock time from another in columns goes wrong unless an hour is exchanged for sixty minutes. Instead hop forward to the next whole hour, then in whole hours, then to the finish, and add the hops. The same method works across midnight, which is where most timetable questions hide their difficulty.
Why time gets its own topic
Because it is the one measure that does not run in tens.
Every other conversion your child meets is a multiplication or division by ten, a hundred or a thousand. Time runs in sixties, and the column methods that work everywhere else quietly fail on it.
Hop to the hour
Do not subtract one time from another. Count on, in convenient hops.
Every hop is easy, and the adding is easy. Compare that with subtracting 14:50 from 16:20 in columns, where the minutes borrow is worth 60 rather than 100 — and a child who borrows a hundred gets 1 hour 70 minutes. That is not how a duration is written — it is really 2 hours 10 minutes — and it is wrong: the answer is 1 hour 30. Column subtraction does work when the exchange is sixty; hopping simply avoids the exchange.
The hops for 14:50 to 16:20.
Across midnight
Same method, in two parts. Up to midnight, then on from midnight.
A shift from 23:40 to 01:15: 23:40 to midnight is 20 minutes. Midnight to 01:15 is 1 hour 15. Together, 1 hour 35 minutes.
Trying to do it as one calculation is where these questions go wrong, and splitting it costs nothing.
The 24-hour clock
Times from 1 p.m. to 11.59 p.m. take twelve added to the hour, and the minutes are untouched. The twelve o'clock hours are the exceptions: 12 noon stays 12:00, and midnight is 00:00, so quarter past midnight is 00:15.
Quarter past seven in the evening is 19:15. Half past eleven at night is 23:30.
And one trap worth naming: 3.5 hours is 3 hours 30 minutes, not 3 hours 50. A decimal in a time means a fraction of an hour, and half of sixty is thirty. This catches children who are comfortable with decimals everywhere else, precisely because everywhere else it would be 50.
Reading a timetable
Most timetables put one service in each column and one stop in each row.
So a single journey is read down a column, and comparing two services is read across a row.
Put a finger on the row and follow it. A slip of one line produces a time that is entirely plausible and completely wrong, which is why it costs marks so reliably.
Where do pupils lose marks?
Subtracting in columns and borrowing a hundred.
Doing a midnight crossing in one step.
Reading 3.5 hours as 3 hours 50 minutes.
Slipping a row on a timetable.
Try it yourself
Count on in hops rather than subtracting. Write each hop down as you make it.
- A train leaves at 14:50 and arrives at 16:20. How long is the journey?
- A shift starts at 23:40 and ends at 01:15. How long is it?
- What is 3.5 hours in minutes?
- What is quarter past seven in the evening on the 24-hour clock?
- Why does subtracting 14:50 from 16:20 in columns go wrong?
- 1 hour 30 minutes. Hop from 14:50 to 15:00, which is 10 minutes. Then 15:00 to 16:00, one hour. Then 16:00 to 16:20, twenty minutes. Total: 1 hour 30.
- 1 hour 35 minutes. Count in two parts: 23:40 to midnight is 20 minutes, then midnight to 01:15 is 1 hour 15. Add them.
- 210 minutes. Three hours is 180, and half an hour is 30. Note that 3.5 hours is not 3 hours 50 minutes, which is the error the decimal invites.
- 19:15. Add twelve to the hour for any time from 1 p.m. onwards, and leave the minutes alone. The twelve o'clock hour is the exception: 12.15 p.m. is 12:15, and 12.15 a.m. is 00:15.
- Because the minutes column does not carry in tens. Taking 50 from 20 requires exchanging one hour for sixty minutes rather than a hundred. A child who borrows a hundred gets 1 hour 70 minutes, which is really 2 hours 10 minutes and the wrong answer. Column subtraction does work when the exchange is sixty; counting on avoids the exchange entirely.
How much practice does this type need at home?
Real journeys. Before you set off, ask how long it will take to get somewhere and what time you will arrive. On the way back, ask how long you were out.
And use a real timetable — a bus stop, a train app, a cinema listing. Ask which service gets there first, and how long the wait is between two of them. That is exactly the question the paper asks, with the advantage that being wrong means missing the bus rather than a mark.
Free: a Maths workbook
Questions across the Maths question types, with the method printed at the top and full answers at the back. One workbook for the whole strand, not a sheet per question type.
Frequently Asked Questions
Why not just subtract the two times?
You can, but only by exchanging an hour for 60 minutes, and ordinary column subtraction exchanges in tens. Taking 14:50 from 16:20 in columns means borrowing from the hours, and the borrow is worth 60 rather than 100. Children who borrow a hundred get answers like 1 hour 70 minutes, which is really 2 hours 10 minutes when the answer should be 1 hour 30. Counting on in hops avoids the borrow entirely, and it is what most adults do without noticing.
What does hopping to the hour mean?
Break the journey at the next whole hour. From 14:50, hop 10 minutes to 15:00. Then take whole hours as far as you can — 15:00 to 16:00 is one hour. Then hop the last bit: 16:00 to 16:20 is 20 minutes. Add the hops: 1 hour 30. Each hop is easy and the adding is easy, which is the point.
How do we handle a time crossing midnight?
In two parts. Up to midnight, then on from midnight. A shift from 23:40 to 01:15 is 20 minutes to midnight plus 1 hour 15 after it — 1 hour 35 altogether. Trying to do it in one calculation is where these go wrong, and splitting it costs nothing.
What catches children out on timetables?
Reading across a row when they should read down a column, or the other way round. A timetable usually has one service per column and one stop per row, so a journey is read down and a comparison between services is read across. It is worth putting a finger on the row and following it, because a slip of one line gives a completely plausible wrong time.
Sources
- GL Assessment — 11+ familiarisation materials and question type descriptions Published 2025.
- Clever Clogs Academy — our own Year 4 and Year 5 lesson records, Winslow Published September 2025 to July 2026.
We are not affiliated with, endorsed by or connected to GL Assessment or Buckinghamshire Council. Test arrangements change; always check the council's own pages for the current year's dates.
We Teach This Method Every Week in Winslow
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