Analysis:
Since there are only three drawers, the probability is 1/3.
Extended data:
Characteristics of classical probability
Limited (only a limited number of all possible basic events)
Equal probability (the probability of each basic event is equal)
Characteristics of basic events
(1) Any two basic events are mutually exclusive.
(2) Any event (except impossible events) can be expressed as the sum of basic events.
Judgment of classical probability
Whether an experiment is a classical probability depends on whether it has two characteristics of classical probability-finiteness and equal possibility. Only the probability with these two characteristics is a classical probability.