User Glorfindel - Mathematics Stack Exchange

16 votes

Prove that for all circle of radius $3^n$ we can have $7^n$ circles inside with a radius of 1

answered Jun 27, 2017 at 13:59

13 votes

Why is the number of ways of choosing $0$ items from $n$ items $1$?

answered Oct 22, 2018 at 13:12

9 votes

What happens when we (incorrectly) make improper fractions proper again?

answered Jul 1, 2020 at 12:33

9 votes

Sleepwalking students on a 9x9 checkerboard

answered Oct 16, 2021 at 7:54

6 votes

Accepted

If $a$ is a repeating decimal, when is $c a$ a terminating decimal? $c\in \mathbb{Z}$

answered Jan 5, 2017 at 14:28

6 votes

Accepted

$N$ is an at most three digit number whose sum of digits equal to the product of its digits. How many possible values of $N$?

answered Apr 22, 2017 at 16:00

6 votes

Why is the roll of a die considered random?

answered May 20, 2017 at 8:17

5 votes

Accepted

The number of solutions to $\cos^2{x}=\cos{2x}.$

answered Apr 30, 2017 at 9:52

5 votes

Accepted

How many secret codes can be made by assigning each letter of the alphabet a (unique) different letter?

answered Dec 1, 2021 at 9:39

5 votes

Accepted

Is this valid Maths?: Given $\frac ab = \frac cd$ does it follow that $a=c$ and $b=d$

answered May 27, 2022 at 8:38

4 votes

Accepted

What would be "tiefliegendes Ergebnis" in English?

answered Dec 12, 2020 at 12:56

4 votes

Accepted

Find $a, b \in \mathbb{Z}_2\times\mathbb{Z}$ with infinite order, that have finite order in the addition (coordinate by coordinate)

answered Jun 27, 2017 at 9:04

4 votes

Computation of $\int^{b}_{a} x^k e^{-x^2} \mathrm{d} x $

answered Jun 27, 2017 at 9:47

4 votes

What is the period of $f(x)=x-[x]$?

answered Mar 15, 2017 at 7:56

4 votes

How do we solve this question without using a calculator?

answered Jan 18, 2017 at 18:21

4 votes

What can be the solution for $y' - 2y = \cos x$?

answered Feb 23, 2017 at 16:45

4 votes

Implication from mod-constraints on a number

answered Jan 11, 2017 at 12:36

4 votes

Accepted

$\tan x$ and $x^2$ derivative

answered Jan 11, 2017 at 16:58

3 votes

If $ \arcsin x+ \arcsin y=\frac{\pi}{2}$, prove that $ x^2+y^2=1$.

answered Aug 8, 2015 at 14:57

3 votes

How to calculate the number of possible combinations?

answered Jul 18, 2015 at 11:43

3 votes

Let $x$ be a real number. Prove that if $x^2\lt x$, then $x\lt1$

answered Feb 6, 2017 at 16:25

3 votes

What is the smallest integer with 100 non trivial factors?

answered Feb 8, 2017 at 18:06

3 votes

Accepted

Order of product of elements of a group

answered Jan 29, 2017 at 11:30

3 votes

Find the sum of floors of roots of a polynomial

answered Jan 14, 2017 at 9:09

3 votes

Accepted

How are these graphs isomorphic?

answered Jan 14, 2017 at 13:27

3 votes

Truth Tables and Implications Query

answered Apr 1, 2017 at 17:48

3 votes

Accepted

Shortest universal bit string: One string to contain all others

answered Apr 15, 2017 at 12:56

3 votes

Accepted

How many binary words of length n are there in which 0 and 1 occur the same number of times and in which no two 0's are adjacent?

answered Apr 16, 2017 at 16:50

3 votes

Accepted

Impossible math - number needs to be divisible and greater than an end result

answered Mar 5, 2017 at 11:43

3 votes

Accepted

If $g$ is an element of order 27 in $G$, does an element of order 3 exist in $G$?

answered Mar 22, 2017 at 20:12

Stack Exchange Network

91 Answers

Prove that for all circle of radius $3^n$ we can have $7^n$ circles inside with a radius of 1

Why is the number of ways of choosing $0$ items from $n$ items $1$?

What happens when we (incorrectly) make improper fractions proper again?

Sleepwalking students on a 9x9 checkerboard

If $a$ is a repeating decimal, when is $c a$ a terminating decimal? $c\in \mathbb{Z}$

$N$ is an at most three digit number whose sum of digits equal to the product of its digits. How many possible values of $N$?

Why is the roll of a die considered random?

The number of solutions to $\cos^2{x}=\cos{2x}.$

How many secret codes can be made by assigning each letter of the alphabet a (unique) different letter?

Is this valid Maths?: Given $\frac ab = \frac cd$ does it follow that $a=c$ and $b=d$

What would be "tiefliegendes Ergebnis" in English?

Find $a, b \in \mathbb{Z}_2\times\mathbb{Z}$ with infinite order, that have finite order in the addition (coordinate by coordinate)

Computation of $\int^{b}_{a} x^k e^{-x^2} \mathrm{d} x $

What is the period of $f(x)=x-[x]$?

How do we solve this question without using a calculator?

What can be the solution for $y' - 2y = \cos x$?

Implication from mod-constraints on a number

$\tan x$ and $x^2$ derivative

If $ \arcsin x+ \arcsin y=\frac{\pi}{2}$, prove that $ x^2+y^2=1$.

How to calculate the number of possible combinations?

Let $x$ be a real number. Prove that if $x^2\lt x$, then $x\lt1$

What is the smallest integer with 100 non trivial factors?

Order of product of elements of a group

Find the sum of floors of roots of a polynomial

How are these graphs isomorphic?

Truth Tables and Implications Query

Shortest universal bit string: One string to contain all others

How many binary words of length n are there in which 0 and 1 occur the same number of times and in which no two 0's are adjacent?

Impossible math - number needs to be divisible and greater than an end result

If $g$ is an element of order 27 in $G$, does an element of order 3 exist in $G$?