12. A wristwatch is 5 minutes slow per hour; 5.5 hours ago they were set to the correct time. Now, on the clock showing the correct time, it is 1 PM. In how many minutes will the wristwatch show 1 PM?
12. In 60 minutes, the hand of the watch "counts" 55 minutes. They need to "count" 5.5 hours. They will do this in 6 hours $\left(\frac{5.5 \cdot 60}{55}=6\right)$. Therefore, 1 hour of the day they will show after 0.5 hours or 30 minutes $(6-5.5=0.5)$.