Test analysis: according to the solution of probability, find two points: the total number of all possible situations; Number of eligible cases; The ratio of the two answers is the probability that it will happen. therefore

There are 3 math books, 2 English books, 5 Chinese books and *** 10 books in the bag.

The probability that a book is a math book is110.

Three copies are 3/ 10.

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.