Units of time
Show on a big screenA film lasts 2 hours. How many minutes is that? How many seconds?
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The idea
A 2-hour film lasts 120 minutes, which is 7200 seconds.
Scientists count time in seconds, written s. This is the SI unit of time. An SI unit is a standard unit scientists share. Bigger units are the minute (min) and the hour (h).
60 s = 1 min. 60 min = 1 h.
- 1 hour.
- 1 hour = 60 minutes.
- 1 hour = 60 minutes = 3600 seconds.
- 1 h = 60 min = 3600 s.
To go from hours to minutes, multiply by 60. To go from minutes to seconds, multiply by 60 again. Each hour has 60 minutes, and each minute has 60 seconds.
2 h = 2 × 60 = 120 min. 120 min = 120 × 60 = 7200 s.
To go back, divide. 7200 s ÷ 60 = 120 min. 120 min ÷ 60 = 2 h.
Long ago in India, a day was 60 ghatis. One ghati was 24 minutes.
Watch out!
A symbol has no s added to make it plural. Write 3 h and 2 min.
Try the lab to finish this lesson.