Seconds to Centuries: How Units of Time Fit Together
What this lesson covers
- 60 seconds make a minute, and a quarter of an hour is 15 minutes.
- 24 hours make a day, and 7 days make a week.
- A year has 52 weeks and 365 days, or 366 days in a leap year, which comes every 4 years.
- A decade is 10 years, a century is 100 years and a millennium is 1,000 years.
Seconds, minutes and hours
- An hour is 60 minutes.
- A quarter of an hour is 60 ÷ 4 = 15 minutes.
| This | Is the same as |
|---|---|
| 1 minute | 60 seconds |
| 1 hour | 60 minutes |
| a quarter of an hour | 15 minutes |
| half an hour | 30 minutes |
| 1 day | 24 hours |
Days, weeks and months
- A week has 7 days.
- A month is about 4 weeks long.
- Months have different numbers of days: 28, 29, 30 or 31.
| Month | Days |
|---|---|
| January | 31 |
| February | 28, or 29 in a leap year |
| March | 31 |
| April | 30 |
| May | 31 |
| June | 30 |
| July | 31 |
| August | 31 |
| September | 30 |
| October | 31 |
| November | 30 |
| December | 31 |
Try it: how many days?
A year and a leap year
- A year has 12 months, 52 weeks and 365 days.
- 52 weeks is 364 days, so a year is 52 weeks and 1 day.
- Every 4 years there is a leap year with 366 days. The extra day is 29 February.
- 2024 and 2028 are leap years.
Decades, centuries and millennia
- Long stretches of time use bigger units.
- A big kauri tree can live for many centuries.
| Unit | Years |
|---|---|
| 1 decade | 10 years |
| 1 century | 100 years |
| 1 millennium | 1,000 years |
Working it out
- Add the same amount again for each unit.
| Question | Think | Answer |
|---|---|---|
| Minutes in 2 hours | 60 + 60 | 120 minutes |
| Seconds in 2 minutes | 60 + 60 | 120 seconds |
| Days in 3 weeks | 7 + 7 + 7 | 21 days |
| Minutes in three quarters of an hour | 15 + 15 + 15 | 45 minutes |
| Years in 3 decades | 10 + 10 + 10 | 30 years |
Try it: match the numbers
Common mistakes
- There are 100 seconds in a minute.There are 60 seconds in a minute.
- A quarter of an hour is 25 minutes, like a quarter of 100.An hour is 60 minutes, so a quarter of an hour is 15 minutes.
- Every month has 30 days.Months have 28 to 31 days. February has 28, or 29 in a leap year.
- A century is 10 years.A decade is 10 years. A century is 100 years.
Your turn
1
How many hours are in a day?
2
How many minutes are in a quarter of an hour?
3
How many days are in a leap year?
4
How many years are in 2 centuries?
5
How many days are in 2 weeks?
Show answer
1. 24 2. 15 3. 366 4. 200 (100 + 100) 5. 14 (7 + 7)
What to take away
- 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day.
- 7 days in a week, 52 weeks and 365 days in a year, 366 in a leap year.
- 10 years in a decade, 100 in a century, 1,000 in a millennium.
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