Which set is FINITE?
A{x ∈ ℕ : x is odd}
B{x ∈ ℕ : 2x − 1 = 0}
C{x ∈ ℕ : (x − 1)(x − 2) = 0}
D{x ∈ ℕ : x is prime}
Answer & Solution
Correct answer: C. {x ∈ ℕ : (x − 1)(x − 2) = 0}
Option A = {1, 2} — finite. Option B = ∅ (2x − 1 = 0 → x = 1/2, not a natural number); ∅ is finite too. But the standard answer treats option A as the unambiguous finite NON-EMPTY set. Option C (primes) and D (odd naturals) are infinite. (Strictly both A and B are finite — typical NCERT exercise emphasises A as 'finite' since B = ∅ counts as 'empty/finite'; in the choice list above A is the unambiguous answer for 'finite non-empty'.)
Related questions
U = {1, 2, ..., 10} and A = {1, 3, 5, 7, 9}. The complement of A is:A = {2, 4, 6, 8} and B = {6, 8, 10, 12}. In A union B the elements 6 and 8 appear:In a Venn diagram the universal set is usually drawn as a:The collection of all subsets of A is called the:How many subsets does {1, 2} have?The open interval (a, b) leaves out:A set with exactly one element is called a:The empty set is a subset of: