Why is it worth writing a time in 24-hour format before applying a time difference?

Because it removes the am and pm labels, leaving a straight addition or subtraction of hours. Writing 2 pm as 14:00 makes subtracting 8 hours a single step, where working in 12-hour time invites a slip between morning and afternoon.

You know a departure time and an arrival time in different time zones. What must you do before finding the journey length?

Put both times into the same time zone first. A journey length is the difference between two clock readings, and a difference only means something when both readings are on the same clock.

How do you find the length of a journey that ends several days after it starts?

Build it up in stages rather than subtracting in one go. Count the minutes to the next full hour, then the hours to the next full day, then the whole days to the arrival date, then the hours and minutes into the final day. Adding those pieces together gives the total, in days, hours and minutes.

A journey includes a stop along the way. How do you find the time actually spent travelling?

Work out the whole time from departure to arrival first, then subtract the stopping time from it. So a total of 24 days 20 hours 35 minutes with an 8 hour stop leaves 24 days 12 hours 35 minutes of actual travelling.

True or False? It does not matter which time zone you use to work out a journey length, as long as you use the same one for both times.

True. A journey length is a difference, and shifting both clock readings by the same number of hours leaves the difference between them unchanged. That is why you are free to convert whichever of the two times is more convenient.

What is the first thing to do with a journey time given as a number of hours, such as 26 hours?

Divide by 24 to split it into whole days and remaining hours . So 26 hours becomes 1 day and 2 hours, and 90 hours becomes 3 days and 18 hours. Splitting it this way lets you change the date first and then worry about the clock.

When adding times, what do you do if the minutes go over 60 or the hours go over 24?

Subtract 60 from the minutes and carry one hour, so 50 + 35 = 85 minutes becomes 1 hour and 25 minutes. Subtract 24 from the hours and carry one day, so 16 + 15 = 31 hours becomes 7 hours on the following date.

Elena leaves at 22:50 on 3 March on a journey of 26 hours 35 minutes, arriving somewhere 1 hour ahead. What is the local arrival time and date?

She arrives at 02:25 on 5 March. 26 hours is 1 day and 2 hours, so the date moves to 4 March at 22:50, and the extra 2 hours carry it to 00:50 on 5 March. Adding the 35 minutes gives 01:25, and the 1 hour time difference makes it 02:25.

A ship arrives at 16:05 on 17 September after a journey of 90 hours 15 minutes, from a place 1 hour behind. When did it leave, local time?

It left at 20:50 on 13 September. 90 hours is 3 days and 18 hours, so take 3 days back to 14 September at 16:05, then 18 hours back to 22:05 on 13 September. Taking off the 15 minutes gives 21:50, and the starting point is 1 hour behind, so its local time was 20:50.

True or False? The time difference can be applied either at the start of the calculation or at the end.

True. Adding a fixed number of hours for the time zone and adding the journey time can be done in either order, because both are simply additions. Do whichever is tidier, but do it once: applying it twice is a common way to lose the answer.

True or False? A journey lasting 26 hours always ends on the day after it started.

False. It depends on the departure time, because 26 hours crosses one midnight for certain but can cross two. Leaving at 22:50 on 3 March, the journey ends at 00:50 on 5 March, which is two days later.

National 5MathsSQAApplications of MathematicsFlashcardsMeasurement SkillsTime Management

Time Management (SQA National 5 Applications of Mathematics): Flashcards

Exam code: X844 75

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FrontTime Zones & Journey Times
Complete the rule for changing between time zones:
If you know the time in the country that is behind, you $______$ the time difference, and if you know the time in the country that is ahead, you $______$ it instead.

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Cards in this collection (16)

Complete the rule for changing between time zones:
If you know the time in the country that is behind, you $______$ the time difference, and if you know the time in the country that is ahead, you $______$ it instead.
The completed rule is:
If you know the time in the country that is behind, you add the time difference, and if you know the time in the country that is ahead, you subtract it instead.
The direction follows from common sense: a country that is ahead has a later time on its clocks.
Why is it worth writing a time in 24-hour format before applying a time difference?
Because it removes the am and pm labels, leaving a straight addition or subtraction of hours.
Writing 2 pm as 14:00 makes subtracting 8 hours a single step, where working in 12-hour time invites a slip between morning and afternoon.
Complete the trick for subtracting 8 hours from 06:00 and crossing back over midnight:
First add $______$ hours to get 30:00, then subtract the 8 hours to reach $______$ on the day before.
The completed trick is:
First add 24 hours to get 30:00, then subtract the 8 hours to reach 22:00 on the day before.
Adding a whole day and then taking it back off in the date is what keeps the arithmetic positive.
It is 20:50 on 13 November in Honolulu, and Edinburgh is 10 hours ahead. What is the time and date in Edinburgh?
It is 06:50 on 14 November in Edinburgh.
Edinburgh is ahead, so add the difference: $20 : 50 + 10 hours = 30 : 50$ .
That is past 24:00, so take 24 hours off the time and add one day to the date.
You know a departure time and an arrival time in different time zones. What must you do before finding the journey length?
Put both times into the same time zone first.
A journey length is the difference between two clock readings, and a difference only means something when both readings are on the same clock.
How do you find the length of a journey that ends several days after it starts?
Build it up in stages rather than subtracting in one go.
Count the minutes to the next full hour, then the hours to the next full day, then the whole days to the arrival date, then the hours and minutes into the final day.
Adding those pieces together gives the total, in days, hours and minutes.
A journey includes a stop along the way. How do you find the time actually spent travelling?
Work out the whole time from departure to arrival first, then subtract the stopping time from it.
So a total of 24 days 20 hours 35 minutes with an 8 hour stop leaves 24 days 12 hours 35 minutes of actual travelling.
True or False?
It does not matter which time zone you use to work out a journey length, as long as you use the same one for both times.
True.
A journey length is a difference, and shifting both clock readings by the same number of hours leaves the difference between them unchanged.
That is why you are free to convert whichever of the two times is more convenient.
What is the first thing to do with a journey time given as a number of hours, such as 26 hours?
Divide by 24 to split it into whole days and remaining hours.
So 26 hours becomes 1 day and 2 hours, and 90 hours becomes 3 days and 18 hours.
Splitting it this way lets you change the date first and then worry about the clock.
When adding times, what do you do if the minutes go over 60 or the hours go over 24?
Subtract 60 from the minutes and carry one hour, so 50 + 35 = 85 minutes becomes 1 hour and 25 minutes.
Subtract 24 from the hours and carry one day, so 16 + 15 = 31 hours becomes 7 hours on the following date.
When subtracting times, what do you do if you need more minutes than you have?
Take off what you can to reach the full hour, then take the rest out of the next hour down.
For 21:30 minus 42 minutes, drop 30 minutes to reach 21:00, leaving 12 to find; $60 - 12 = 48$ , so the answer is 20:48.
Elena leaves at 22:50 on 3 March on a journey of 26 hours 35 minutes, arriving somewhere 1 hour ahead. What is the local arrival time and date?
She arrives at 02:25 on 5 March.
26 hours is 1 day and 2 hours, so the date moves to 4 March at 22:50, and the extra 2 hours carry it to 00:50 on 5 March.
Adding the 35 minutes gives 01:25, and the 1 hour time difference makes it 02:25.
Complete the order for adding a journey time to a departure time:
Add the full $______$ first, then the remaining hours, and the $______$ last of all.
The completed order is:
Add the full days first, then the remaining hours, and the minutes last of all.
Working from the largest unit down means each carry lands in a part you have not dealt with yet, so nothing has to be revisited.
A ship arrives at 16:05 on 17 September after a journey of 90 hours 15 minutes, from a place 1 hour behind. When did it leave, local time?
It left at 20:50 on 13 September.
90 hours is 3 days and 18 hours, so take 3 days back to 14 September at 16:05, then 18 hours back to 22:05 on 13 September.
Taking off the 15 minutes gives 21:50, and the starting point is 1 hour behind, so its local time was 20:50.
True or False?
The time difference can be applied either at the start of the calculation or at the end.
True.
Adding a fixed number of hours for the time zone and adding the journey time can be done in either order, because both are simply additions.
Do whichever is tidier, but do it once: applying it twice is a common way to lose the answer.
True or False?
A journey lasting 26 hours always ends on the day after it started.
False.
It depends on the departure time, because 26 hours crosses one midnight for certain but can cross two.
Leaving at 22:50 on 3 March, the journey ends at 00:50 on 5 March, which is two days later.

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