What is the size of the obtuse angle between the clock hands at 930?

At 9:30, the minute hand is on the 6 (180 degrees), and the hour hand is halfway between the 9 and 10 (which is 285 degrees). To find the smaller angle between the two hands, subtract the smaller angle from the larger one: 285 - 180 = 105 degrees. The obtuse angle, which is the larger angle, is 360 - 105 = 255 degrees. Thus, the size of the obtuse angle between the clock hands at 9:30 is 255 degrees.