In the 4× 100-meter relay race of the school's autumn track and field meeting, the runway is arranged by lottery, and there are three classes (1), (2) and (3) in the third grade.

Question 1:. So

Question 1:. Solution: (1) The tree diagram lists all possible results:

Question 2:(2)∫ There are six possible outcomes, and the possibility of each outcome is equal, among which (1) and (2).

There are only 1 shift in the first and second lanes.

∴ = .

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