$3-$ $[$ Motion Problems $]$

On Monday at noon (12:00), the clock showed the correct time, but after 4 hours, it was 1 hour behind.

On which day and at what hour will these clocks first show a time that is 1 hour ahead of the actual time?
For the first time, the clock will show one hour more when it falls behind by 23 hours. Since it falls behind by 1 hour every 4 hours, this will happen after 

$23 \cdot 4=92$ hours. Since $92=24 \cdot 3+20$, three days and 20 hours will pass.

## Answer

On the coming Friday at 8:00.