A watch, which gains 5 seconds in 3 minutes was set right at 7 a.m. In the afternoon of the same day, when the correct time is 4 p.m., what time will be indicated by that watch?

It is clear that the watch gains 5 seconds in every 3 minutes, and the number of hours between 7a.m to 4:00 p.m. is = 9 hours, i.e. 9 * 60 = 540 minutes. So, according to this, the watch will gain 540 minutes = 540 * 5 / 3 = 900 seconds and 900 seconds = 900 / 60 = 15 minutes. Thus, the watch will gain 15 minutes in 9 hours. Therefore, the time indicated by the watch at 4 p.m. = 4.00 + 0:15 = 4:15 pm.