9. Sleepy Flies (7th grade. 1 point). One day in October, Nikita glanced at the clock hanging on the wall and saw that four flies had fallen asleep on the clock face. The first one was sleeping precisely at the 12 mark, while the others were also precisely positioned at the 3, 6, and 9 marks.

- How beautiful! - Nikita marveled and even felt sorry for the flies, noticing that the hour hand posed no threat to them, but the minute hand would definitely sweep them all away one by one.

Find the probability that exactly 20 minutes after Nikita looked at the clock, two flies had already been swept away.
Solution. The event "exactly 2 flies are swatted" occurs only if at the moment when Petya looked at the clock, the minute hand was between 11 and 12 o'clock, 2 and 3 o'clock, 5 and 6 o'clock, or 8 and 9 o'clock. It is not hard to notice that in total these intervals amount to 4 hours, which covers exactly $\frac{1}{3}$ of the clock face.

Answer: $\frac{1}{3}$.