Working with time and time zones · Usually met around P6
Start, finish and time taken
Count in pieces, or turn it all into minutes.
How to do it
Method
Count in pieces, or turn it all into minutes
09:50 → 10:00 → 11:25: 10 + 85 = 95 minutes
Another way
All in minutes
685 − 590 = 95
In full
Know two of the three and you can find the third: finish = start + time taken; start = finish − time taken; time taken = finish − start. The 24-hour clock makes it easiest. To find the time taken, count in pieces: 09:50 to 10:00 is 10 minutes, 10:00 to 11:25 is 1 hour 25 minutes, 1 hour 35 minutes in all. Or change everything into minutes and subtract: 11:25 is 685 minutes, 09:50 is 590, and 685 − 590 = 95 minutes. Careful: 60 minutes carry into an hour, and when the minutes won't take away, borrow 60 from the hours; times can't be taken away like decimals (11.25 − 9.50 is wrong). Past midnight into the next day, count to 24:00 first, then add the next day's time.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Starting at 09:30, 1 hour 15 minutes later it is □ hours □ minutes (24-hour clock).
Fill in each box
Show the answer and working
Answer: 10，45
09:30 + 1 hour 15 minutes = 10:45: every 60 minutes carry into an hour.
Example 2
An event ended at 18:45 after 1 hour 10 minutes. It started at □ hours □ minutes (24-hour clock).
Fill in each box
Show the answer and working
Answer: 17，35
Start = finish − time taken: 18:45 − 1 hour 10 minutes = 17:35; when the minutes won't take away, borrow 60.
Example 3
Starting at 14:55, 50 minutes later it is 16:25.
True or false?
Show the answer and working
Answer: False
The minutes pass 60, so carry an hour: 15:45.
Practise it in the game →Working with time and time zones · Free to start, unlimited questions, no download