Given Data

1. Clock gain rate: Gains 5 minutes every 1 hour.
2. Clock set correctly at: 8:00 AM.

Question

What time will the clock show at 8:00 PM on the same day?

Answer

9:00 PM.

Solution

1. Calculate actual time elapsed between 8:00 AM and 8:00 PM = 12 hours.
2. For every 1 hour of true time, the clock runs for 1 hour 5 minutes = 65 minutes.
3. In 12 true hours, clock indicates = 12 × 65 minutes = 780 minutes.
4. Convert 780 minutes into hours = 780 / 60 = 13 hours.
5. Adding 13 hours to 8:00 AM gives 9:00 PM.
6. Therefore, the faulty clock will display 9:00 PM.