Year 4: Units of time: seconds, minutes, hours, days and weeks
Part of the Year 4 telling the time and the 24-hour clock chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Units of time: seconds, minutes, hours, days and weeks
We measure time in lots of different units. Short times are in seconds and minutes. Longer times are in hours, days, weeks, months and years. Here is how they fit together:
The facts to know: 60 seconds = 1 minute | 60 minutes = 1 hour | 24 hours = 1 day | 7 days = 1 week | 12 months = 1 year.
Big unit to small unit: multiply. There are more small units than big units. 3 hours is 3 × 60 = 180 minutes. A table helps:
| hours | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| minutes | 60 | 120 | 180 | 240 | 300 |
Small unit to big unit: divide. There are fewer big units. 240 minutes is 240 ÷ 60 = 4 hours. If something is left over, it is the remainder: 135 minutes = 2 hours and 15 minutes left over, because 2 × 60 = 120 and 135 − 120 = 15.
Mixed units. To change 3 hours 20 minutes to minutes, change the hours first (3 × 60 = 180) and then add the 20 minutes: 180 + 20 = 200 minutes.
Parts of an hour. Half an hour is 30 minutes. A quarter of an hour is 15 minutes. Three quarters of an hour is 45 minutes. So 1½ hours is 60 + 30 = 90 minutes.
Key ideas
- 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year.
- Big unit to small unit: multiply. Small unit to big unit: divide.
- When you divide, the remainder is the small units left over: 135 minutes = 2 hours 15 minutes.
- Mixed units: change the big unit first, then add the small units.
- Half an hour = 30 minutes, a quarter of an hour = 15 minutes. 1½ hours = 90 minutes.
- There are 60 minutes in an hour, not 100.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from minutes to seconds (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Multiply by 60. We have 5 minutes, so we need 5 lots of 60.5 × 60 = 5 × 6 × 10 = 30 × 10 = 300
- Write the answer with its unit. 5 minutes = 300 seconds
Check. Go back: 300 ÷ 60 = 5. ✓
Watch out. A big unit changes to a bigger number of small units. 5 minutes must be more than 5 seconds.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from hours to minutes (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Multiply by 60. We have 3 hours, so we need 3 lots of 60.3 × 60 = 3 × 6 × 10 = 18 × 10 = 180
- Write the answer with its unit. 3 hours = 180 minutes
Check. Go back: 180 ÷ 60 = 3. ✓
Watch out. A big unit changes to a bigger number of small units. 3 hours must be more than 3 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 24 hours in 1 day. Going from days to hours (big unit to small unit), we multiply by 24.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 day = 24 hours
- Multiply by 24. We have 6 days, so we need 6 lots of 24.6 × 24 = 6 × 20 + 6 × 4 = 120 + 24 = 144
- Write the answer with its unit. 6 days = 144 hours
Check. Go back: 144 ÷ 24 = 6. ✓
Watch out. A big unit changes to a bigger number of small units. 6 days must be more than 6 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from weeks to days (big unit to small unit), we multiply by 7.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Multiply by 7. We have 5 weeks, so we need 5 lots of 7.5 × 7 = 35 (a times-table fact)
- Write the answer with its unit. 5 weeks = 35 days
Check. Go back: 35 ÷ 7 = 5. ✓
Watch out. A big unit changes to a bigger number of small units. 5 weeks must be more than 5 days.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from seconds to minutes (small unit to big unit), we divide by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Divide by 60. Going from seconds to minutes (small unit to big unit) we divide. We find how many lots of 60 are in 420.420 ÷ 60 = 42 ÷ 6 = 7 (divide by 10, then by 6)
- Write the answer with its unit. 420 seconds = 7 minutes
Check. 7 × 60 = 420 = 420. ✓
Watch out. A small unit changes to a smaller number of big units. 420 seconds must be fewer than 420 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 240.240 ÷ 60 = 24 ÷ 6 = 4 (divide by 10, then by 6)
- Write the answer with its unit. 240 minutes = 4 hours
Check. 4 × 60 = 240 = 240. ✓
Watch out. A small unit changes to a smaller number of big units. 240 minutes must be fewer than 240 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60. The remainder is the left over minutes.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 135.60 × 2 = 120
60 × 3 = 180 is too big
135 − 120 = 15 left over
135 ÷ 60 = 2 remainder 15 - Write the whole hours and the left over minutes. The remainder is the minutes that do not make another whole h.135 minutes = 2 hours 15 minutes
Check. 2 × 60 = 120 and 120 + 15 = 135. ✓
Watch out. The remainder is minutes, not a decimal. 135 minutes is not 2.15 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from days to weeks (small unit to big unit), we divide by 7. The remainder is the left over days.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Divide by 7. Going from days to weeks (small unit to big unit) we divide. We find how many lots of 7 are in 23.7 × 3 = 21
7 × 4 = 28 is too big
23 − 21 = 2 left over
23 ÷ 7 = 3 remainder 2 - Write the whole weeks and the left over days. The remainder is the days that do not make another whole week.23 days = 3 weeks 2 days
Check. 3 × 7 = 21 and 21 + 2 = 23. ✓
Watch out. The remainder is days, not a decimal. 23 days is not 3.2 weeks.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the hours into minutes first. Then add the minutes you already have.
- Change 3 hours into minutes. 1 h = 60 minutes, so multiply by 60.3 × 60 = 3 × 6 × 10 = 18 × 10 = 180
- Add the 20 minutes. Now we add on the minutes that were left.180 + 20 = 200
- Write the answer with its unit. 3 hours 20 minutes = 200 minutes
Check. 200 ÷ 60 = 3 remainder 20, which is 3 hours 20 minutes. ✓
Watch out. There are 60, not 100, minutes in a h.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the whole hours to minutes, then find the fraction of a h and add.
- Change the 1 whole hour into minutes. 1 h = 60 minutes.1 × 60 = 60
- Find the fraction of a h. 12 of 60 means divide 60 into 2 equal parts.60 ÷ 2 = 30
12 of a h = 30 minutes - Add the parts together. 60 + 30 = 90 minutes
Check. Check: 90 ÷ 60 = 1.5 hours. ✓
Watch out. Half an hour is 30 minutes, so 1½ hours is 90 minutes, not 1 hour 50 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. To compare two times, change them to the same unit. Then compare the numbers.
- Change 2 hours into minutes. We can only compare when both are in the same unit.2 × 60 = 120 minutes
- Write the other time in minutes. 100 minutes is already in minutes.100 minutes
- Compare the numbers. The bigger number is the longer time.120 is bigger than 100.
The longer time is 2 hours.
Check. 2 hours = 120 minutes and 100 minutes = 100 minutes. ✓
Watch out. Do not compare the numbers 2 and 100 without changing the units. They are different units!
Watch out
1.5 hours is not 1 hour 50 minutes. The number after the point is not minutes. 1.5 hours means 1 and a half hours, so it is 1 hour and 30 minutes (90 minutes). And an hour has 60 minutes, not 100, so 2.25 hours is not 2 hours 25 minutes. Always change to minutes using 60.Exercise 8D Changing units of time
Non-calculatorKey words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from hours to minutes (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Multiply by 60. We have 2 hours, so we need 2 lots of 60.2 × 60 = 2 × 6 × 10 = 12 × 10 = 120
- Write the answer with its unit. 2 hours = 120 minutes
Check. Go back: 120 ÷ 60 = 2. ✓
Watch out. A big unit changes to a bigger number of small units. 2 hours must be more than 2 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from hours to minutes (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Multiply by 60. We have 5 hours, so we need 5 lots of 60.5 × 60 = 5 × 6 × 10 = 30 × 10 = 300
- Write the answer with its unit. 5 hours = 300 minutes
Check. Go back: 300 ÷ 60 = 5. ✓
Watch out. A big unit changes to a bigger number of small units. 5 hours must be more than 5 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from hours to minutes (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Multiply by 60. We have 7 hours, so we need 7 lots of 60.7 × 60 = 7 × 6 × 10 = 42 × 10 = 420
- Write the answer with its unit. 7 hours = 420 minutes
Check. Go back: 420 ÷ 60 = 7. ✓
Watch out. A big unit changes to a bigger number of small units. 7 hours must be more than 7 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from hours to minutes (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Multiply by 60. We have 12 hours, so we need 12 lots of 60.12 × 60 = 12 × 6 × 10 = 72 × 10 = 720
- Write the answer with its unit. 12 hours = 720 minutes
Check. Go back: 720 ÷ 60 = 12. ✓
Watch out. A big unit changes to a bigger number of small units. 12 hours must be more than 12 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from minutes to seconds (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Multiply by 60. We have 3 minutes, so we need 3 lots of 60.3 × 60 = 3 × 6 × 10 = 18 × 10 = 180
- Write the answer with its unit. 3 minutes = 180 seconds
Check. Go back: 180 ÷ 60 = 3. ✓
Watch out. A big unit changes to a bigger number of small units. 3 minutes must be more than 3 seconds.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from minutes to seconds (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Multiply by 60. We have 6 minutes, so we need 6 lots of 60.6 × 60 = 6 × 6 × 10 = 36 × 10 = 360
- Write the answer with its unit. 6 minutes = 360 seconds
Check. Go back: 360 ÷ 60 = 6. ✓
Watch out. A big unit changes to a bigger number of small units. 6 minutes must be more than 6 seconds.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from minutes to seconds (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Multiply by 60. We have 10 minutes, so we need 10 lots of 60.10 × 60 = 10 × 6 × 10 = 60 × 10 = 600
- Write the answer with its unit. 10 minutes = 600 seconds
Check. Go back: 600 ÷ 60 = 10. ✓
Watch out. A big unit changes to a bigger number of small units. 10 minutes must be more than 10 seconds.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from minutes to seconds (big unit to small unit), we multiply by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Multiply by 60. We have 15 minutes, so we need 15 lots of 60.15 × 60 = 15 × 6 × 10 = 90 × 10 = 900
- Write the answer with its unit. 15 minutes = 900 seconds
Check. Go back: 900 ÷ 60 = 15. ✓
Watch out. A big unit changes to a bigger number of small units. 15 minutes must be more than 15 seconds.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 120.120 ÷ 60 = 12 ÷ 6 = 2 (divide by 10, then by 6)
- Write the answer with its unit. 120 minutes = 2 hours
Check. 2 × 60 = 120 = 120. ✓
Watch out. A small unit changes to a smaller number of big units. 120 minutes must be fewer than 120 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 240.240 ÷ 60 = 24 ÷ 6 = 4 (divide by 10, then by 6)
- Write the answer with its unit. 240 minutes = 4 hours
Check. 4 × 60 = 240 = 240. ✓
Watch out. A small unit changes to a smaller number of big units. 240 minutes must be fewer than 240 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 420.420 ÷ 60 = 42 ÷ 6 = 7 (divide by 10, then by 6)
- Write the answer with its unit. 420 minutes = 7 hours
Check. 7 × 60 = 420 = 420. ✓
Watch out. A small unit changes to a smaller number of big units. 420 minutes must be fewer than 420 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 600.600 ÷ 60 = 60 ÷ 6 = 10 (divide by 10, then by 6)
- Write the answer with its unit. 600 minutes = 10 hours
Check. 10 × 60 = 600 = 600. ✓
Watch out. A small unit changes to a smaller number of big units. 600 minutes must be fewer than 600 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 24 hours in 1 day. Going from days to hours (big unit to small unit), we multiply by 24.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 day = 24 hours
- Multiply by 24. We have 2 days, so we need 2 lots of 24.2 × 24 = 2 × 20 + 2 × 4 = 40 + 8 = 48
- Write the answer with its unit. 2 days = 48 hours
Check. Go back: 48 ÷ 24 = 2. ✓
Watch out. A big unit changes to a bigger number of small units. 2 days must be more than 2 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 24 hours in 1 day. Going from days to hours (big unit to small unit), we multiply by 24.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 day = 24 hours
- Multiply by 24. We have 4 days, so we need 4 lots of 24.4 × 24 = 4 × 20 + 4 × 4 = 80 + 16 = 96
- Write the answer with its unit. 4 days = 96 hours
Check. Go back: 96 ÷ 24 = 4. ✓
Watch out. A big unit changes to a bigger number of small units. 4 days must be more than 4 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from weeks to days (big unit to small unit), we multiply by 7.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Multiply by 7. We have 3 weeks, so we need 3 lots of 7.3 × 7 = 21 (a times-table fact)
- Write the answer with its unit. 3 weeks = 21 days
Check. Go back: 21 ÷ 7 = 3. ✓
Watch out. A big unit changes to a bigger number of small units. 3 weeks must be more than 3 days.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from weeks to days (big unit to small unit), we multiply by 7.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Multiply by 7. We have 8 weeks, so we need 8 lots of 7.8 × 7 = 56 (a times-table fact)
- Write the answer with its unit. 8 weeks = 56 days
Check. Go back: 56 ÷ 7 = 8. ✓
Watch out. A big unit changes to a bigger number of small units. 8 weeks must be more than 8 days.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from days to weeks (small unit to big unit), we divide by 7. The remainder is the left over days.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Divide by 7. Going from days to weeks (small unit to big unit) we divide. We find how many lots of 7 are in 16.7 × 2 = 14
7 × 3 = 21 is too big
16 − 14 = 2 left over
16 ÷ 7 = 2 remainder 2 - Write the whole weeks and the left over days. The remainder is the days that do not make another whole week.16 days = 2 weeks 2 days
Check. 2 × 7 = 14 and 14 + 2 = 16. ✓
Watch out. The remainder is days, not a decimal. 16 days is not 2.2 weeks.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from days to weeks (small unit to big unit), we divide by 7. The remainder is the left over days.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Divide by 7. Going from days to weeks (small unit to big unit) we divide. We find how many lots of 7 are in 29.7 × 4 = 28
7 × 5 = 35 is too big
29 − 28 = 1 left over
29 ÷ 7 = 4 remainder 1 - Write the whole weeks and the left over days. The remainder is the days that do not make another whole week.29 days = 4 weeks 1 day
Check. 4 × 7 = 28 and 28 + 1 = 29. ✓
Watch out. The remainder is days, not a decimal. 29 days is not 4.1 weeks.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from days to weeks (small unit to big unit), we divide by 7. The remainder is the left over days.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Divide by 7. Going from days to weeks (small unit to big unit) we divide. We find how many lots of 7 are in 45.7 × 6 = 42
7 × 7 = 49 is too big
45 − 42 = 3 left over
45 ÷ 7 = 6 remainder 3 - Write the whole weeks and the left over days. The remainder is the days that do not make another whole week.45 days = 6 weeks 3 days
Check. 6 × 7 = 42 and 42 + 3 = 45. ✓
Watch out. The remainder is days, not a decimal. 45 days is not 6.3 weeks.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in 1 week. Going from days to weeks (small unit to big unit), we divide by 7. The remainder is the left over days.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 week = 7 days
- Divide by 7. Going from days to weeks (small unit to big unit) we divide. We find how many lots of 7 are in 60.7 × 8 = 56
7 × 9 = 63 is too big
60 − 56 = 4 left over
60 ÷ 7 = 8 remainder 4 - Write the whole weeks and the left over days. The remainder is the days that do not make another whole week.60 days = 8 weeks 4 days
Check. 8 × 7 = 56 and 56 + 4 = 60. ✓
Watch out. The remainder is days, not a decimal. 60 days is not 8.4 weeks.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the hours into minutes first. Then add the minutes you already have.
- Change 2 hours into minutes. 1 h = 60 minutes, so multiply by 60.2 × 60 = 2 × 6 × 10 = 12 × 10 = 120
- Add the 20 minutes. Now we add on the minutes that were left.120 + 20 = 140
- Write the answer with its unit. 2 hours 20 minutes = 140 minutes
Check. 140 ÷ 60 = 2 remainder 20, which is 2 hours 20 minutes. ✓
Watch out. There are 60, not 100, minutes in a h.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the hours into minutes first. Then add the minutes you already have.
- Change 3 hours into minutes. 1 h = 60 minutes, so multiply by 60.3 × 60 = 3 × 6 × 10 = 18 × 10 = 180
- Add the 5 minutes. Now we add on the minutes that were left.180 + 5 = 185
- Write the answer with its unit. 3 hours 5 minutes = 185 minutes
Check. 185 ÷ 60 = 3 remainder 5, which is 3 hours 5 minutes. ✓
Watch out. There are 60, not 100, minutes in a h.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the minutes into seconds first. Then add the seconds you already have.
- Change 1 minute into seconds. 1 min = 60 seconds, so multiply by 60.1 × 60 = 1 × 6 × 10 = 6 × 10 = 60
- Add the 45 seconds. Now we add on the seconds that were left.60 + 45 = 105
- Write the answer with its unit. 1 minute 45 seconds = 105 seconds
Check. 105 ÷ 60 = 1 remainder 45, which is 1 minute 45 seconds. ✓
Watch out. There are 60, not 100, seconds in a min.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the weeks into days first. Then add the days you already have.
- Change 4 weeks into days. 1 week = 7 days, so multiply by 7.4 × 7 = 28 (a times-table fact)
- Add the 3 days. Now we add on the days that were left.28 + 3 = 31
- Write the answer with its unit. 4 weeks 3 days = 31 days
Check. 31 ÷ 7 = 4 remainder 3, which is 4 weeks 3 days. ✓
Watch out. There are 7, not 100, days in a week.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60. The remainder is the left over minutes.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 125.60 × 2 = 120
60 × 3 = 180 is too big
125 − 120 = 5 left over
125 ÷ 60 = 2 remainder 5 - Write the whole hours and the left over minutes. The remainder is the minutes that do not make another whole h.125 minutes = 2 hours 5 minutes
Check. 2 × 60 = 120 and 120 + 5 = 125. ✓
Watch out. The remainder is minutes, not a decimal. 125 minutes is not 2.5 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60. The remainder is the left over minutes.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 200.60 × 3 = 180
60 × 4 = 240 is too big
200 − 180 = 20 left over
200 ÷ 60 = 3 remainder 20 - Write the whole hours and the left over minutes. The remainder is the minutes that do not make another whole h.200 minutes = 3 hours 20 minutes
Check. 3 × 60 = 180 and 180 + 20 = 200. ✓
Watch out. The remainder is minutes, not a decimal. 200 minutes is not 3.20 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 seconds in 1 min. Going from seconds to minutes (small unit to big unit), we divide by 60. The remainder is the left over seconds.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 min = 60 seconds
- Divide by 60. Going from seconds to minutes (small unit to big unit) we divide. We find how many lots of 60 are in 150.60 × 2 = 120
60 × 3 = 180 is too big
150 − 120 = 30 left over
150 ÷ 60 = 2 remainder 30 - Write the whole minutes and the left over seconds. The remainder is the seconds that do not make another whole min.150 seconds = 2 minutes 30 seconds
Check. 2 × 60 = 120 and 120 + 30 = 150. ✓
Watch out. The remainder is seconds, not a decimal. 150 seconds is not 2.30 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 24 hours in 1 day. Going from hours to days (small unit to big unit), we divide by 24. The remainder is the left over hours.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 day = 24 hours
- Divide by 24. Going from hours to days (small unit to big unit) we divide. We find how many lots of 24 are in 50.24 × 2 = 48
24 × 3 = 72 is too big
50 − 48 = 2 left over
50 ÷ 24 = 2 remainder 2 - Write the whole days and the left over hours. The remainder is the hours that do not make another whole day.50 hours = 2 days 2 hours
Check. 2 × 24 = 48 and 48 + 2 = 50. ✓
Watch out. The remainder is hours, not a decimal. 50 hours is not 2.2 days.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the whole hours to minutes, then find the fraction of a h and add.
- Find the fraction of a h. 12 of 60 means divide 60 into 2 equal parts.60 ÷ 2 = 30
12 of a h = 30 minutes - Write the answer. 30 minutes
Check. Check: 30 ÷ 60 = 0.5 hours. ✓
Watch out. Half an hour is 30 minutes, so 1½ hours is 90 minutes, not 1 hour 50 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the whole hours to minutes, then find the fraction of a h and add.
- Find the fraction of a h. 14 of 60 means divide 60 into 4 equal parts.60 ÷ 4 = 15
14 of a h = 15 minutes - Write the answer. 15 minutes
Check. Check: 15 ÷ 60 = 0.25 hours. ✓
Watch out. Half an hour is 30 minutes, so 1½ hours is 90 minutes, not 1 hour 50 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the whole hours to minutes, then find the fraction of a h and add.
- Change the 1 whole hour into minutes. 1 h = 60 minutes.1 × 60 = 60
- Find the fraction of a h. 12 of 60 means divide 60 into 2 equal parts.60 ÷ 2 = 30
12 of a h = 30 minutes - Add the parts together. 60 + 30 = 90 minutes
Check. Check: 90 ÷ 60 = 1.5 hours. ✓
Watch out. Half an hour is 30 minutes, so 1½ hours is 90 minutes, not 1 hour 50 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change the whole hours to minutes, then find the fraction of a h and add.
- Change the 2 whole hours into minutes. 1 h = 60 minutes.2 × 60 = 120
- Find the fraction of a h. 34 of 60 means divide 60 into 4 equal parts and take 3.60 ÷ 4 = 15, then 3 × 15 = 45
- Add the parts together. 120 + 45 = 165 minutes
Check. Check: 165 ÷ 60 = 2.75 hours. ✓
Watch out. Half an hour is 30 minutes, so 1½ hours is 90 minutes, not 1 hour 50 minutes.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. To compare two times, change them to the same unit. Then compare the numbers.
- Change 2 hours into minutes. We can only compare when both are in the same unit.2 × 60 = 120 minutes
- Write the other time in minutes. 100 minutes is already in minutes.100 minutes
- Compare the numbers. The bigger number is the longer time.120 is bigger than 100.
2 hours > 100 minutes
Check. 2 hours = 120 minutes and 100 minutes = 100 minutes. ✓
Watch out. Do not compare the numbers 2 and 100 without changing the units. They are different units!
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. To compare two times, change them to the same unit. Then compare the numbers.
- Change 3 minutes into seconds. We can only compare when both are in the same unit.3 × 60 = 180 seconds
- Write the other time in seconds. 200 seconds is already in seconds.200 seconds
- Compare the numbers. The bigger number is the longer time.200 is bigger than 180.
3 minutes < 200 seconds
Check. 3 minutes = 180 seconds and 200 seconds = 200 seconds. ✓
Watch out. Do not compare the numbers 2 and 100 without changing the units. They are different units!
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. To compare two times, change them to the same unit. Then compare the numbers.
- Change 2 days into hours. We can only compare when both are in the same unit.2 × 24 = 48 hours
- Write the other time in hours. 50 hours is already in hours.50 hours
- Compare the numbers. The bigger number is the longer time.50 is bigger than 48.
2 days < 50 hours
Check. 2 days = 48 hours and 50 hours = 50 hours. ✓
Watch out. Do not compare the numbers 2 and 100 without changing the units. They are different units!
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 h. Going from minutes to hours (small unit to big unit), we divide by 60. The remainder is the left over minutes.
- Write the fact. We need to know how many of the small unit make one of the big unit.1 h = 60 minutes
- Divide by 60. Going from minutes to hours (small unit to big unit) we divide. We find how many lots of 60 are in 95.60 × 1 = 60
60 × 2 = 120 is too big
95 − 60 = 35 left over
95 ÷ 60 = 1 remainder 35 - Write the whole hours and the left over minutes. The remainder is the minutes that do not make another whole h.95 minutes = 1 hour 35 minutes
Check. 1 × 60 = 60 and 60 + 35 = 95. ✓
Watch out. The remainder is minutes, not a decimal. 95 minutes is not 1.35 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Multiply the minutes each day by 7 days. Then change the minutes into hours and minutes.
- Find the minutes in a week. Zainab practises 20 minutes on each of 7 days.7 × 20 = 7 × 2 × 10 = 14 × 10 = 140 minutes
- Change 140 minutes into hours. 60 minutes make 1 hour.60 × 2 = 120
60 × 3 = 180 is too big
140 − 120 = 20 left over - Write the answer. 140 minutes = 2 hours 20 minutes
Check. 2 × 60 + 20 = 140. ✓
Watch out. Remember to change minutes into hours using 60, not 100.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 7 days in a week. Multiply the hours of sleep each day by 7.
- Write the sum. The baby sleeps 14 hours on each of 7 days.7 × 14
- Split 14 to make it easier. 14 = 10 + 4.7 × 10 = 70 and 7 × 4 = 28
- Add the answers. 70 + 28 = 98 hours
Check. 98 ÷ 7 = 14. ✓
Watch out. Use 7 days in a week.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change 1.5 hours properly. The .5 means a half, not 50 minutes.
- Look at what Aisha said. 1.5 hours = 1 hour 50 minutes.Aisha: 1 hour 50 minutes
- Find the mistake. She treated the 5 as 50 minutes. But .5 is a half of an hour, and an hour has 60 minutes, not 100.half of 60 = 60 ÷ 2 = 30 minutes
- Write the right answer. 1.5 hours = 1 hour + 30 minutes = 1 hour 30 minutes (90 minutes)
Check. 1 hour 30 minutes = 60 + 30 = 90 minutes, and half way between 1 hour and 2 hours is 90 minutes. ✓
Watch out. .5 of an hour is 30 minutes. 1 hour 50 minutes is more than 1.75 hours.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. Change weeks to days and compare with what Noah said.
- Change 3 weeks into days. 1 week = 7 days.3 × 7 = 21 days
- Compare with 20 days. Noah said 20.21 is not 20.
- Explain. Noah is not right. 20 days is 2 weeks 6 days, which is 1 day less than 3 weeks.20 ≠ 21
Check. 21 ÷ 7 = 3 weeks. ✓
Watch out. Use the 7 times table: 7, 14, 21.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 60 minutes in 1 hour and 60 seconds in 1 minute. Use both facts.
- Find the seconds in a minute. This fact we know.1 minute = 60 seconds
- Find the minutes in an hour. This fact we know too.1 hour = 60 minutes
- Multiply the two facts. 60 minutes in an hour, and each minute has 60 seconds.60 × 60 = 6 × 6 × 100 = 36 × 100 = 3,600 seconds
Check. 3,600 ÷ 60 = 60 minutes. ✓
Watch out. Think of 60 groups of 60.
Key words. To convert is to change from one unit to another. 60 seconds = 1 minute. 60 minutes = 1 hour. 24 hours = 1 day. 7 days = 1 week. 12 months = 1 year. To go from a big unit to a small unit we multiply. To go from a small unit to a big unit we divide.
Method. There are 24 hours in a day and 60 minutes in each hour. Multiply the two facts.
- Write the facts. 24 hours in a day and 60 minutes in an hour.1 day = 24 hours, 1 hour = 60 minutes
- Multiply. We need 24 lots of 60.24 × 60 = 24 × 6 × 10 = 144 × 10 = 1,440 minutes
Check. 1,440 ÷ 60 = 24. ✓
Watch out. 24 × 6 = 144, then multiply by 10.