Year 6: Converting units of time
Part of the Year 6 area, volume and measures chapter. Chapter overview · whole chapter on one page
Converting units of time
Time is measured in hours, minutes and seconds. There are 60 minutes in 1 hour and 60 seconds in 1 minute. Sometimes we write part of an hour as a decimal, so 30 minutes is 0.5 hours and 45 minutes is 0.75 hours.
To change hours to minutes, multiply by 60. To change minutes to hours, divide by 60. To change hours and minutes to a decimal, change the minutes to a fraction of an hour first, then add the whole hours.
Key ideas
- 1 hour = 60 minutes, so 1 hour = 60 min.
- 1 minute = 60 seconds.
- 0.5 hours = 30 minutes, 0.25 hours = 15 minutes, 0.75 hours = 45 minutes.
- 2 hours 15 minutes = 2.25 hours, because 15 minutes is 0.25 of an hour.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Multiply the hours by 60 to get minutes.
- Remember: 1 hour = 60 minutes. So each hour gives 60 minutes.1 h = 60 min
- Multiply the hours by 60. This gives the number of minutes.1.75 × 60 = 105
- Write the answer. The answer is in minutes.105
Check. 105 ÷ 60 = 1.75 hours. ✓
Watch out. Multiply by 60 to go from hours to minutes. Do not multiply by 100.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Divide the minutes by 60 to get hours.
- Remember: 60 minutes = 1 hour. So we divide the minutes by 60.60 min = 1 h
- Divide the minutes by 60. This gives the number of hours, written as a decimal.45 ÷ 60 = 0.75
- Write the answer. The answer is in hours.0.75
Check. 0.75 × 60 = 45 minutes. ✓
Watch out. Divide by 60 to go from minutes to hours. For example, 30 minutes is half of an hour, so it is 0.5 hours.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Change the minutes to hours with a decimal, then add the whole hours.
- Change the minutes to a fraction of an hour. Each minute is one sixtieth of an hour.15 ÷ 60 = 0.25
- Add the whole hours. The whole hours stay the same.2 + 0.25 = 2.25
- Write the answer. The answer is in hours, as a decimal.2.25
Check. 2.25 hours is 2 hours and 15 minutes: 15 ÷ 60 = 0.25. ✓
Watch out. Do not write 2 h 15 min as 2.15. The 15 minutes is a quarter of an hour, so it is 0.25.
Watch out
Common mistake: 2 hours 15 minutes is not 2.15 hours. The 15 minutes is a quarter of an hour, which is 0.25, so the answer is 2.25 hours.
Exam tip
Ask yourself: how many 60s are in the time? A decimal of an hour is a part of 60 minutes, so 0.5 is 30 minutes.
Exercise 9B Converting time
Non-calculatorKey words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Multiply the hours by 60 to get minutes.
- Remember: 1 hour = 60 minutes. So each hour gives 60 minutes.1 h = 60 min
- Multiply the hours by 60. This gives the number of minutes.2.5 × 60 = 150
- Write the answer. The answer is in minutes.150
Check. 150 ÷ 60 = 2.5 hours. ✓
Watch out. Multiply by 60 to go from hours to minutes. Do not multiply by 100.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Multiply the hours by 60 to get minutes.
- Remember: 1 hour = 60 minutes. So each hour gives 60 minutes.1 h = 60 min
- Multiply the hours by 60. This gives the number of minutes.3.25 × 60 = 195
- Write the answer. The answer is in minutes.195
Check. 195 ÷ 60 = 3.25 hours. ✓
Watch out. Multiply by 60 to go from hours to minutes. Do not multiply by 100.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Multiply the hours by 60 to get minutes.
- Remember: 1 hour = 60 minutes. So each hour gives 60 minutes.1 h = 60 min
- Multiply the hours by 60. This gives the number of minutes.0.4 × 60 = 24
- Write the answer. The answer is in minutes.24
Check. 24 ÷ 60 = 0.4 hours. ✓
Watch out. Multiply by 60 to go from hours to minutes. Do not multiply by 100.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Multiply the minutes by 60 to get seconds.
- Remember: 1 minute = 60 seconds. So each minute gives 60 seconds.1 min = 60 s
- Multiply the minutes by 60. This gives the number of seconds.2.5 × 60 = 150
- Write the answer. The answer is in seconds.150
Check. 150 ÷ 60 = 2.5 minutes. ✓
Watch out. Multiply by 60, because there are 60 seconds in each minute.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Divide the minutes by 60 to get hours.
- Remember: 60 minutes = 1 hour. So we divide the minutes by 60.60 min = 1 h
- Divide the minutes by 60. This gives the number of hours, written as a decimal.30 ÷ 60 = 0.5
- Write the answer. The answer is in hours.0.5
Check. 0.5 × 60 = 30 minutes. ✓
Watch out. Divide by 60 to go from minutes to hours. For example, 30 minutes is half of an hour, so it is 0.5 hours.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Divide the minutes by 60 to get hours.
- Remember: 60 minutes = 1 hour. So we divide the minutes by 60.60 min = 1 h
- Divide the minutes by 60. This gives the number of hours, written as a decimal.27 ÷ 60 = 0.45
- Write the answer. The answer is in hours.0.45
Check. 0.45 × 60 = 27 minutes. ✓
Watch out. Divide by 60 to go from minutes to hours. For example, 30 minutes is half of an hour, so it is 0.5 hours.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Change the minutes to hours with a decimal, then add the whole hours.
- Change the minutes to a fraction of an hour. Each minute is one sixtieth of an hour.30 ÷ 60 = 0.5
- Add the whole hours. The whole hours stay the same.1 + 0.5 = 1.5
- Write the answer. The answer is in hours, as a decimal.1.5
Check. 1.5 hours is 1 hours and 30 minutes: 30 ÷ 60 = 0.5. ✓
Watch out. Do not write 2 h 15 min as 2.15. The 15 minutes is a quarter of an hour, so it is 0.25.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Change the minutes to hours with a decimal, then add the whole hours.
- Change the minutes to a fraction of an hour. Each minute is one sixtieth of an hour.45 ÷ 60 = 0.75
- Add the whole hours. The whole hours stay the same.3 + 0.75 = 3.75
- Write the answer. The answer is in hours, as a decimal.3.75
Check. 3.75 hours is 3 hours and 45 minutes: 45 ÷ 60 = 0.75. ✓
Watch out. Do not write 2 h 15 min as 2.15. The 15 minutes is a quarter of an hour, so it is 0.25.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Multiply the hours by 60 to get minutes.
- Remember: 1 hour = 60 minutes. So each hour gives 60 minutes.1 h = 60 min
- Multiply the hours by 60. This gives the number of minutes.1.25 × 60 = 75
- Write the answer. The answer is in minutes.75
Check. 75 ÷ 60 = 1.25 hours. ✓
Watch out. Multiply by 60 to go from hours to minutes. Do not multiply by 100.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Change the train journey to minutes, then compare it with the bus journey.
- Change the train journey to minutes. There are 60 minutes in 1 hour.2.5 × 60 = 150 minutes
- Find the difference between the two journeys. The bus is longer, so take the train away from the bus.165 - 150 = 15
- Write the answer. The answer is in minutes.15
Check. 150 + 15 = 165 minutes. ✓
Watch out. Both journeys must be in minutes before you compare them.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Change the minutes and seconds into seconds, then add them.
- Change the 3 minutes into seconds. There are 60 seconds in 1 minute.3 × 60 = 180 seconds
- Add the 20 seconds. The seconds are added to the seconds from the minutes.180 + 20 = 200
- Write the answer. The answer is in seconds.200
Check. 200 seconds is 3 minutes and 20 seconds, because 3 × 60 = 180 and 180 + 20 = 200. ✓
Watch out. Do not write 3 minutes 20 seconds as 3.20. Change to seconds first.
Key words. There are 60 minutes in 1 hour and 60 seconds in 1 minute. A decimal hour uses a decimal point: 30 minutes is 0.5 hours, because 30 is half of 60.
Method. Change 0.6 hours into minutes, then compare with 60 minutes.
- Change 0.6 hours into minutes. Multiply the hours by 60.0.6 × 60 = 36 minutes
- Compare the answer with 60 minutes. Tom said 60 minutes, so the two must match.36 minutes is not 60 minutes
- Write the answer. Tom is not right.No
Check. 0.6 is more than half of an hour, so it is more than 30 minutes, but it is less than 60 minutes. ✓
Watch out. Half an hour is 0.5, not 0.6. Check your decimal using the number line above.