A defective clock is set right at 11:00 am. If it is known that it gains three minutes per hour, then what will be the correct time when it shows 9:30 pm on the same day?

The faulty clock shows 10 hours and 30 minutes have passed, which equals 10.5 hours on the faulty clock, and it gained 3 minutes per hour during this period. The ratio of real time to faulty time is 60 divided by 63, so the actual elapsed time is 10.5 multiplied by 60 and then divided by 63, resulting in 10 hours. Adding 10 hours to the 11 am start time gives the true time of 9 pm.

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