A clock loses exactly ten minutes every hour. If the clock is set correctly at noon, what is the correct time when the clock reads 3:00pm?
3:36pm. For every 60 minutes of real time, the clock moves 50 minutes. Put another way, 60/50 = 1.2 real minutes per slow-clock minute.
In order for the clock to show 3:00pm, 180 of its slow minutes have to pass. 1.2 * 180 clock minutes = 216 real minutes or 3 hours and 36 minutes.