for Grandson David on the Occasion of His Twelfth Birthday
have probably heard this really old children's riddle...
The clock that loses one minute per day will show the correct time only once every 720 days (that's almost two years!), whereas a clock that does not run at all will be right twice a day (groan).
you have a clock or a watch with a sweep-second hand? You will see here
a picture of my favorite clock and a simple puzzle that goes with it...