Clock Gain Problem

Time indicated from 10 AM to 3 PM next day $= 29$ hours. Clock gains 10 minutes per 24 hours $= \frac{10}{24}$ minutes per hour. In 29 hours, gain $\approx 12.08$ minutes.

True time $= 3\text{ PM} - 12.08\text{ mins} \approx 2\text{ PM } 48\text{ minutes}$.