A shelf in a public library contains 100 books, 40 mathematics textbooks and 60 basic technology textbooks. A textbook is chosen at random from the shelf. Find the probability of selecting: a) A mathematics textbook. b) A basic technology textbook. c) Either a mathematics or a basic technology textbook.

Step 1: Identify the total number of books and the number of books for each category.
Total number of books on the shelf = 100
Number of mathematics textbooks = 40
Number of basic technology textbooks = 60

Step 2: Calculate the probability for part a).
The probability of selecting a mathematics textbook is the number of mathematics textbooks divided by the total number of books.

$$P(\text{Mathematics}) = \frac{\text{Number of mathematics textbooks}}{\text{Total number of books}}$$ $$P(\text{Mathematics}) = \frac{40}{100}$$ $$P(\text{Mathematics}) = \frac{2}{5} = 0.4$$