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Measurement › Time
Time
Reading clocks, counting minutes, and working with durations — base 60 instead of base 10.
Read the clock
Slide the hands. The face moves with you.
3:15
That's quarter past 3
The clock dial
- The short hand points at the hour.
- The long hand points at the minutes.
- Each number on the face is 5 minutes apart for the long hand.
Common phrases
- Quarter past 3 = 3:15
- Half past 3 = 3:30
- Quarter to 4 = 3:45
Why base 60?
The Babylonians used base 60 because 60 has lots of divisors (2, 3, 4, 5, 6, 10, 12, 15, 20, 30). It makes thirds and quarters of an hour come out as whole numbers of minutes.
Durations
To find how long from 9:45 to 11:20: count up to 10:00 (15 min), then to 11:00 (1 hour), then to 11:20 (20 min). Total: 1 h 35 min.