Mark M. answered 09/14/16
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To arrive at a formula AM and PM must be eliminated. Only a 24 hour clock works.
1 hour on X clock equals 24 hours.
60 minutes on X clock equals 24 hours.
10 minutes on X clock equals 4 hours
2.5 minutes on X clock equals 1 hour
3 PM is 15 hours after midnight on a 24 hour clock.
15(2.5) = 37.5
X:37.5 is the same as 3 PM.
For X:20
20/2.5 = 8
X:20 = 08:00, or 8 AM