Find the sum of the books in the bag, and then find the probability that any one is a math book.

The number of books in the bag is 3+2+5= 10 (book), including 3 math books.

So the probability of choosing a math book is 3/ 10.

Take any book in the bag, and every book is equally likely to be taken away.

Extended data:

Multiplication and division of fractions

1, the fraction is multiplied by the integer, the denominator remains the same, the numerator is multiplied by the integer, and finally the score that can be reduced is reported.

2. The score is multiplied by the score, the numerator is multiplied by the numerator, and the denominator is multiplied by the denominator, and finally the offer score that can be reduced is obtained.

3. Fraction divided by integer, denominator unchanged. If the numerator is a multiple of an integer, divide the numerator by the integer, and finally you can reduce the number of offer points.

4. Fraction divided by integer, denominator unchanged. If the numerator is not a multiple of an integer, multiply this score by the reciprocal of the integer, and finally the offer score can be reduced.

5, the score divided by the score is equal to the dividend multiplied by the reciprocal of the divisor, and finally the offer score that can be reduced.