Step-by-step Maths Level 4: Finding how long between two times
Part of the Step-by-step Maths Level 4 time to the minute chapter. Chapter overview · whole chapter on one page
Finding how long between two times
To find how long between two times, count on in steps. First count the minutes to the next hour, then the whole hours, then the last minutes.
To find an end time, add the duration to the start time. Carry the minutes into the hours when they pass 60.
Key ideas
- Count on in steps: minutes to the hour, whole hours, then minutes.
- Add a duration to find the end time.
- When minutes pass 60, add an hour.
Method. Count on from the start time to the end time, in steps: minutes to the hour, whole hours, then minutes.
- Count the minutes to the next hour. Count on to 15:00.20 to 14:20 is 40 minutes to 15:00
- Count the minutes after the hour. Count on from 15:00 to 15:05.5 minutes
- Add the parts. Add the minutes together.40 + 5 = 45
- Write the duration. The duration is 45 minutes.45 minutes
Check. Check: 14:20 plus 45 minutes is 15:05.
Watch out. Count on in minutes, not in hours.
Method. Count on from the start time to the end time, in steps.
- Count the minutes to 10:00. Count on from 9:50 to 10:00.10 minutes
- Count the hour from 10:00 to 11:00. One full hour.1 hour
- Count the minutes after 11:00. Count on from 11:00 to 11:10.10 minutes
- Add the parts. Add the parts together.10 + 60 + 10 = 80 minutes
- Write the duration. 80 minutes is 1 hour 20 minutes.1 hour 20 minutes
Check. Check: 9:50 plus 1 hour 20 minutes is 11:10.
Watch out. Do not subtract 11 from 9 and 10 from 50.
Method. Add the length of the film to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.13:15
- Add the hour first. One hour after 13:15 is 14:15.13:15 + 1 hour = 14:15
- Add the 40 minutes. 14:15 plus 40 minutes is 14:55.14:15 + 40 minutes = 14:55
- Write the finish time. Use two digits for the hour and minutes.14:55
Check. Check: 14:55 minus 1 hour 40 minutes is 13:15.
Watch out. Add the hours first, then the minutes.
Watch out
Watch out. From 9:50 to 11:10 is 1 hour 20 minutes, not 2 hours. Count the minutes to 10:00 first, then the rest.
Exam tip
Grown-up tip. Use a clock face or a number line from the start time. Count on, and ask: “How many minutes so far?”
Exercise 8E Practice: durations and end times
Non-calculatorMethod. Add the length of the activity to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.17:41
- Add the duration. Add 2 hours to the start time.17:41 + 2 hours = 19:41
- Write the finish time. Use two digits for the hour and minutes.19:41
Check. Check: 2 hours before 19:41 is 17:41.
Watch out. When the minutes go past 60, add one hour and take away 60 minutes.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 21:00. Count on to the next full hour.20:20 to 21:00 is 40 minutes
- Count the whole hours up to 20:00. Each full hour is 60 minutes.-1 hours = -60 minutes
- Count the minutes from 20:00 to 20:49. Count on the last minutes.49 minutes
- Add the parts. Add the minutes from each part.40 + -60 + 49 = 29
- Write the duration. Give the answer in hours and minutes.29 minutes
Check. Check: 20:20 plus 29 minutes is 20:49.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Add the length of the activity to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.09:21
- Add the duration. Add 1 hour to the start time.09:21 + 1 hour = 10:21
- Write the finish time. Use two digits for the hour and minutes.10:21
Check. Check: 1 hour before 10:21 is 09:21.
Watch out. When the minutes go past 60, add one hour and take away 60 minutes.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 15:00. Count on to the next full hour.14:55 to 15:00 is 5 minutes
- Count the whole hours up to 15:00. Each full hour is 60 minutes.0 hours = 0 minutes
- Count the minutes from 15:00 to 15:55. Count on the last minutes.55 minutes
- Add the parts. Add the minutes from each part.5 + 0 + 55 = 60
- Write the duration. Give the answer in hours and minutes.1 hour
Check. Check: 14:55 plus 1 hour is 15:55.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 11:00. Count on to the next full hour.10:30 to 11:00 is 30 minutes
- Count the whole hours up to 14:00. Each full hour is 60 minutes.3 hours = 180 minutes
- Count the minutes from 14:00 to 14:18. Count on the last minutes.18 minutes
- Add the parts. Add the minutes from each part.30 + 180 + 18 = 228
- Write the duration. Give the answer in hours and minutes.3 hours 48 minutes
Check. Check: 10:30 plus 3 hours 48 minutes is 14:18.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Add the length of the activity to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.14:11
- Add the duration. Add 1 hour 20 minutes to the start time.14:11 + 1 hour 20 minutes = 15:31
- Write the finish time. Use two digits for the hour and minutes.15:31
Check. Check: 1 hour 20 minutes before 15:31 is 14:11.
Watch out. When the minutes go past 60, add one hour and take away 60 minutes.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 09:00. Count on to the next full hour.08:42 to 09:00 is 18 minutes
- Count the whole hours up to 09:00. Each full hour is 60 minutes.0 hours = 0 minutes
- Count the minutes from 09:00 to 09:33. Count on the last minutes.33 minutes
- Add the parts. Add the minutes from each part.18 + 0 + 33 = 51
- Write the duration. Give the answer in hours and minutes.51 minutes
Check. Check: 08:42 plus 51 minutes is 09:33.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 18:00. Count on to the next full hour.17:46 to 18:00 is 14 minutes
- Count the whole hours up to 19:00. Each full hour is 60 minutes.1 hour = 60 minutes
- Count the minutes from 19:00 to 19:21. Count on the last minutes.21 minutes
- Add the parts. Add the minutes from each part.14 + 60 + 21 = 95
- Write the duration. Give the answer in hours and minutes.1 hour 35 minutes
Check. Check: 17:46 plus 1 hour 35 minutes is 19:21.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the whole hours up to 20:00. Each full hour is 60 minutes.2 hours = 120 minutes
- Count the minutes from 20:00 to 20:00. Count on the last minutes.0 minutes
- Add the parts. Add the minutes from each part.0 + 120 + 0 = 120
- Write the duration. Give the answer in hours and minutes.2 hours
Check. Check: 18:00 plus 2 hours is 20:00.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 18:00. Count on to the next full hour.17:21 to 18:00 is 39 minutes
- Count the whole hours up to 19:00. Each full hour is 60 minutes.1 hour = 60 minutes
- Count the minutes from 19:00 to 19:26. Count on the last minutes.26 minutes
- Add the parts. Add the minutes from each part.39 + 60 + 26 = 125
- Write the duration. Give the answer in hours and minutes.2 hours 5 minutes
Check. Check: 17:21 plus 2 hours 5 minutes is 19:26.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Add the length of the activity to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.13:51
- Add the duration. Add 1 hour 45 minutes to the start time.13:51 + 1 hour 45 minutes = 15:36
- Write the finish time. Use two digits for the hour and minutes.15:36
Check. Check: 1 hour 45 minutes before 15:36 is 13:51.
Watch out. When the minutes go past 60, add one hour and take away 60 minutes.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 10:00. Count on to the next full hour.09:10 to 10:00 is 50 minutes
- Count the whole hours up to 09:00. Each full hour is 60 minutes.-1 hours = -60 minutes
- Count the minutes from 09:00 to 09:35. Count on the last minutes.35 minutes
- Add the parts. Add the minutes from each part.50 + -60 + 35 = 25
- Write the duration. Give the answer in hours and minutes.25 minutes
Check. Check: 09:10 plus 25 minutes is 09:35.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 18:00. Count on to the next full hour.17:57 to 18:00 is 3 minutes
- Count the whole hours up to 20:00. Each full hour is 60 minutes.2 hours = 120 minutes
- Count the minutes from 20:00 to 20:29. Count on the last minutes.29 minutes
- Add the parts. Add the minutes from each part.3 + 120 + 29 = 152
- Write the duration. Give the answer in hours and minutes.2 hours 32 minutes
Check. Check: 17:57 plus 2 hours 32 minutes is 20:29.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Count on from the start time to the end time, in steps: minutes to the next hour, whole hours, then minutes.
- Count the minutes to the next hour, 20:00. Count on to the next full hour.19:13 to 20:00 is 47 minutes
- Count the whole hours up to 23:00. Each full hour is 60 minutes.3 hours = 180 minutes
- Count the minutes from 23:00 to 23:04. Count on the last minutes.4 minutes
- Add the parts. Add the minutes from each part.47 + 180 + 4 = 231
- Write the duration. Give the answer in hours and minutes.3 hours 51 minutes
Check. Check: 19:13 plus 3 hours 51 minutes is 23:04.
Watch out. Count the minutes to the next hour first. Do not subtract the hours and the minutes separately.
Method. Add the length of the activity to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.14:48
- Add the duration. Add 2 hours to the start time.14:48 + 2 hours = 16:48
- Write the finish time. Use two digits for the hour and minutes.16:48
Check. Check: 2 hours before 16:48 is 14:48.
Watch out. When the minutes go past 60, add one hour and take away 60 minutes.
Method. Add the length of the activity to the start time. Carry extra minutes into the hours.
- Write the start time. It is where we begin.15:25
- Add the duration. Add 1 hour 30 minutes to the start time.15:25 + 1 hour 30 minutes = 16:55
- Write the finish time. Use two digits for the hour and minutes.16:55
Check. Check: 1 hour 30 minutes before 16:55 is 15:25.
Watch out. When the minutes go past 60, add one hour and take away 60 minutes.