Time Zones & Journey Times (SQA National 5 Applications of Mathematics): Revision Note
Exam code: X844 75
Time zones
How do I find times using different time zones?
You will be given the time difference between two time zones in your exam question
Most time differences are full hours
e.g. Hong Kong is 8 hours ahead of Edinburgh
If you know the time in the country that is behind
add the time difference to find the time in the other country
e.g. 2 pm in Edinburgh is 10 pm in Hong Kong
If you know the time in the country that is ahead
subtract the time difference to find the time in the other country
e.g. 2 pm in Hong Kong is 6 am in Edinburgh
Examiner Tips and Tricks
Writing your time in the 24 hour format can help. For example, 2 pm is 14:00. This makes it easier to subtract 8 hours.
Be careful crossing midnight. One trick is to add 24 hours to your time first. For example, to subtract 8 hours from 06:00:
first add 24 hours to get 30:00
then subtract 8 hours to get 22:00
The time would be 10 pm and the date would be the day before.
Worked Example
Edinburgh is 10 hours ahead of Honolulu.
Edinburgh is 2 hours behind Athens.
It is 8:50 pm local time on 13 November in Honolulu.
Find the local time and date in Athens.
Answer:
Write the time in 24-hour format
8:50 pm = 20:50
Find the local time in Edinburgh
Add the time difference as Edinburgh is ahead
Subtract 24 from the hours and add 1 to the day
20:50 + 10 hours = 30:50
06:50 on 14 November
Find the local time in Athens
Add the time difference as Athens is ahead
06:50 + 2 hours = 08:50
14 November 08:50 or 8:50 am
Journey times
How do I find the time of a journey?
You might have to find the journey time given:
the departure time
the arrival time
You need to find the difference between the departure time and arrival time
You need to start with the departure time and build up to the arrival time
Steps
STEP 1
Convert the departure time or arrival time using the time differenceIt does not matter which time zone you use
But they must both use the same time zone
STEP 2
Start with the departure time and find the number of minutes until the next full hourSTEP 3
Find the number of hours until the next full daySTEP 4
Find the number of days until the date of arrivalSTEP 5
Find the number of hours until the arrival hourSTEP 6
Find the number of hours until the arrival hourSTEP 7
Add together the time intervals from the previous steps
What do I do if there is stopping time?
Sometimes a person might stop at a location for a period of time during the journey
They might be taking two flights and stop at the airport between the flights
You might be asked to either:
find the stopping time given the journey times
or find the length of a journey given the stopping time
The steps for both:
Find the time between the departure time and arrival time
Subtract the other time that you are given in the question
Worked Example
Oli sails from Aberdeen to Honolulu.
Oli departs Aberdeen at 4:40 pm local time on 4 December.
Oli arrives in San Francisco and stops for 8 hours before departing.
Oli arrives in Honolulu at 3:15 am local time on 29 December.
Aberdeen is 10 hours ahead of Honolulu.
Calculate the total time that Oli spends sailing. Give your answer using days, hours and minutes.
Answer:
Find the departure time in Honolulu time
Subtract the time difference as Honolulu is behind
4:40 pm = 16:40
16:40 - 10 hours = 06:40
Start with the departure time and find the time to the arrival time
Find the minutes to the next full hour
06:40 to 07:00
60 minutes - 40 minutes = 20 minutes
Find the hours to the next full day
4 December 07:00 to 5 December 00:00
24 hours - 7 hours = 17 hours
Find the days to the arrival date
5 December to 29 December
29 days - 5 days = 24 days
Find the hours and minutes to the arrival hour
00:00 to 03:15 is 3 hours and 15 minutes
Add together the times
20 minutes + 15 minutes = 35 minutes
17 hours + 3 hours = 20 hours
24 days 20 hours 35 minutes
Subtract the stopping time
20 hours - 8 hours = 12 hours
24 days 12 hours 35 minutes
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