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