Every hour, the minute hand goes 360 degrees and the hour hand 30 degrees, so X hours = minute hand gains 330 times X degrees. To gain exactly 180 degrees that's 180 / 330 hrs, or 60 x 180 / 330 minutes. That is, 32 minutes and 43 7/11 seconds.. doesn't even depends on whether you start at the hands at the 3 o'clock or the 9 o'clock position.