Is $\mathbb Q \times \mathbb Q $ a denumerable set?
27937
Cartesian Product of Two Countable Sets is Countable
40162
Prove that the set $\mathbb{Q}[\alpha] = \{a+b\alpha+c\alpha^2 \mid a, b, c \in\mathbb{Q}\}$ is closed under addition and multiplication.
75068
subgroups of $\mathbb Z / 2 \mathbb Z \times \mathbb Z / 2 \mathbb Z$
62566
Does $X\times S^1\cong Y\times S^1$ imply that $X\times\mathbb R\cong Y\times\mathbb R$?
21431
The set of all functions from $\mathbb{N} \to \{0, 1\}$ is uncountable?
85032
$Q(\mathbb{Z}[t]) / \mathbb{Z}[t]$ is not injective
35626
Is $(\mathbb{R}^2, lexicographic) \cong (\mathbb{R}, discrete)\times (\mathbb{R}, usual)$?
92740
prove that $\mathbb{Q}^n$is dense subset of $\mathbb{R^n}$
72420
Is $\mathbb{N}$ impossible to pin down?
36325
Embedding ordinals in $\mathbb{Q}$
60359
Proving that these two sets are denumerable.
68490
For $x\in\mathbb R\setminus\mathbb Q$, the set $\{nx-\lfloor nx\rfloor: n\in \mathbb{N}\}$ is dense on $[0,1)$
40937
Is the set of partial order relations over $ \mathbb{N}$ countable?
155125
Every ordered field has a subfield isomorphic to $\mathbb Q$?
145039
Algebraic independence over $\overline{\mathbb Q}$ and over $\mathbb Q$
45991
Why $f\colon \mathbb{Z}_n^\times \to \mathbb{Z}_m^\times$ is surjective?
120035
Pattern in Isomorphisms between $\mathbb Z_m \times \mathbb Z_n$ and $\mathbb Z_{mn}$