A wall clock gains 4 minutes every hour. It is set to the correct time at 6 a.m. What time will this clock show at the moment when the correct time is 3 p.m. on the same day?

From 6 a.m. to 3 p.m. is 9 hours of true time. Gaining 4 minutes in each of those hours means the clock runs $9\times 4=36$ minutes ahead, so it shows 3:36 p.m. The traps: 3:32 p.m. comes from counting only 8 hours, 3:04 p.m. from adding the 4 minutes just once, and 2:24 p.m. from treating a gaining clock as a losing one.