You work at the watch counter in Best’s. Two Swatch watches in the case are acting up, so you isolate them for study. You find that one of them loses two minutes per hour, and the other one gains one minute per hour. This means that in one hour of real time, one watch goes 58 minutes and the other goes 61 minutes. Now, you start both watches running at exactly twelve noon. If you look at them again when the faster watch is exactly one hour ahead of the slower watch, what time will it be in real time?
The faster watch “gains” 3 minutes on the slower watch each hour, so it will be an hour ahead in 20 hours, at 8 am. At that time, the slower watch, having lost 2 minutes per hour, will read 7:20; the faster watch, having gained 1 minute per hour, will read 8:20.