3 hours . . . 6 minutes . . . 45 seconds
+ 8 hours . . 55 minutes . . . 20 seconds
________________________________
11 hours . . 61 minutes . . . 65 seconds
But 65 seconds = 1 minute . . . 5 seconds
11 hours . . 62 minutes . . . 5 seconds
But 62 minutes = 1 hour . . . 2 minutes
12 hours . . 2 minutes . . . 5 seconds
I think this is regrouping, but with 60s instead of 10s.
