Question

Identify the infinite sets among the following.

• A. {$x:x\in Z$, -60 < $x$ < 60}
• B. {…., -5, -4, -3, -2, .....}
• C. The set of letters in the English alphabet.
• D. {$x:x\in W$, $x$ > 20}

Answer 1

Answer: (B), (D)

The correct options are
B {…., -5, -4, -3, -2, .....}
D {$x:x\in W$, $x$ > 20}

{$x:x\in Z$, -60 < $x$ < 60} $\to$ There are finite number of integers between -60 and 60. It is a finite set.

{…., -5, -4, -3, -2, ....} $\to$ There are infinite number of integers less than -5. It is an infinite set.

The set of letters in the English alphabet. $\to$ There are 26 letters in the English alphabet. It is a finite set.

{$x:x\in W$, $x$ > 20} $\to$ There are infinite number of whole numbers which are greater than 20. It is an infinite set.