Analysis: 1: When he came back from work, the clock ran 21:00-12:10 = 8 hours and 50 minutes. 8 hours and 50 minutes minus 8 hours at work minus 65438+ 00 minutes early equals 40 minutes on the road. One-way time 40 minutes divided by 2 equals 20 minutes.
2. He arrived at the factory at 14: 50 (15 minus 10 minus 20 minutes on the way 14: 50 equals 14: 30. 14: 30-12:10 = 2 hours and 20 minutes, the stop time of the clock.