Hours Match the Minutes Divided by Five

A clock is base 12 (a 12 hour clock) and base 60 (an hour contains 60 minutes). Since they are divisible by each other you can use minute markers only to tell the hour by looking at the position of the hour in minutes and dividing by 5. For example, at the 15 minute position the hour is 3. At the 30 minute position the hour is 6 and so on.

See also:

• Antikythera Mechanism models the sun, moon, and planets of ancient Greece