# Tagged Questions

Questions about numbers expressible as the quotient of two integers. For questions on determining whether a number is rational, use the (rationality-testing) tag instead.

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### Pugh's exercise on Dedekind cuts addition

I am trying to solve the following exercise: Let $x=A|B$ and $x'=A'|B'$ be cuts in $\mathbb{Q}$. Show that although $B+B'$ is disjoint from $A+A'$, it may happen in degenerate cases that $\mathbb{Q}$ ...
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### How to Find a rational number between two irratonal number? [on hold]

Find the rational number between $\sqrt 2$ and $\sqrt3$. I try to solve by using some methods in my book but can not understand steeps.
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### Rational numbers problem [on hold]

I have a problem with rational numbers, how do i find the numbers behind the following equation: 0,a(b) = a/b, using the following rationale: a/b*10=a,(...
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### Are there any natural proofs of irrationality using the decimal characterization?

Mathematicians typically define rational number to mean quotient of two integers. It is not hard to show that a number is rational by that definition if and only if its decimal expansion terminates ...
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### Algorithm that calculates decimal places of number

My background. I am a school student. Recently, we learned about rational numbers and irrational numbers. For example, we were told that rational numbers can always be written as a repeating decimal, ...
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### Is $\pi e$ irrational? [duplicate]

During our ongoing research, we need to prove that $\pi e<\lceil \pi e\rceil$. Is $\pi e$ irrational? How to prove it? Thanks- mike
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### Prove that there are exactly $k$ pairs $(x,y)$ of rational numbers with $0\leq x,y<1$ for which both $ax+by,cx+dy$ are integers.

Let $a,b,c,d$ are integers such that $(a,b)=(c,d)=1$ and $ad-bc=k>0$. Prove that there are exactly $k$ pairs $(x,y)$ of rational numbers with $0\leq x,y<1$ for which both $ax+by,cx+dy$ are ...
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### Is $x^x$ rational for $x=\sqrt{2}^\sqrt{2}$

This might be naive. Is $x^x$ a rational number for $x=\sqrt{2}^\sqrt{2}$ ? I remember reading somewhere a long time ago that such $x^x$ is a rational number, as an example of issues with non-...
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### Rational root coefficient

I saw this question in my exam recently, If a, b, c are distinct rational roots of $x^3+ax^2+bx+c=0$, find the values of a, b, c. Can someone give me a hint or answer? I tried factoring it and ...
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### nearest approximation for a/b with denominator less than n

Given a rational number a/b what is the closest ration c/d such that d I would like a formula for c and d in terms of a,b and n if possible but if no mathematical solution exists, an algorithm for ...
### Let $H = \{2^m : m \in \mathbb{Z}\}$ & define a relation $R$ on the set $\mathbb{Q^{+}}$ of positive rationals by $a\mathbin{R}b$ iff $a/b \in H$.
Let $H = \{2^m : m \in \mathbb{Z}\}$ and define a relation $R$ on the set $\mathbb{Q^{+}}$ of positive rational numbers by $a\mathbin{R}b$ if and only if $a/b \in H$. Prove that $R$ is an equivalence ...