Exercises on Section 2

Let A be the set of integers between 100 and 999 inclusive.

• (a) Express A in the form A = {x ∈ ?? : condition}

• (b) What is the cardinality of A?

If B = {s ∈ SeqOfChar : s starts with ‘T’ and s has length 4}, which of the following is a member of the set B?

• (a) “This”.

• (b) [‘T’, ‘h’, ‘i’, ‘s’, ‘.’].

• (c) [“T”, “h”, “i”, “s”].

Suppose that each possible time of the day is stored as a pair of integers, where the first integer gives the hour and the second integer gives the minute. For example, (14, 45) represents a quarter to three in the afternoon. (Midnight is (0, 0) rather than (24, 00).) Express the set of possible times of the day in the form {(h, m) ∈ ?? : condition}.