Let $r$ be a rational no. with $0<r<1$. Then $r$ can be expressed as a sum of reciprocals of finitely many distinct positive integers
86497
Prove that any rational can be expressed in the form $\sum\limits_{k=1}^n{\frac{1}{a_k}}$, $a_k\in\mathbb N^*$
143271
Finite sum of reciprocal odd integers
101835
Which rationals can be written as the sum of two rational squares?
90076
Prove that every positive integer $n$ is a unique product of a square and a squarefree number
122914
An integer $n$, such that $nx = 0$, where $x$ belongs to the quotient group $\Bbb Q/\Bbb Z$
83145
Sum of rational numbers
15187
Integer reciprocals in arithmetic progression
22890
Is it coherent to extend $\mathbb{R}$ with a reciprocal of $0$?
69288
Number of real roots of $\sum_{k=0}^{n}\frac{x^{k}}{k!}=0$
59391
$p,q,r$ primes, $\sqrt{p}+\sqrt{q}+\sqrt{r}$ is irrational.
29780
If $x$ is a positive rational but not an integer, is $x^x$ irrational?
42444
Irrationality of $\sum_{p\in\mathbb{P}} \frac{1}{2^{p}}$
86988
Cardinality of the Irrationals
53244
Prove that $p \in \mathbb{R}[x]$ can be represented as a sum of squares of polynomials from $\mathbb{R}[x]$
32848
Prove that the product of a non-zero rational and irrational number is irrational.
59535
Prove that there exists such a set of $n$ positive integers
135750
Prove that if a and b are integers, then there are unique integers q and r such that $a = bq + r$, $-|b|/2 < r \le |b|/2$