Question

Let $A$ be a set of $n$ residues $\pmod{n^{2}}$. Prove that there exists a set $B$ of of $n$ residues $\pmod{n^{2}}$ ...

score 217 · Answer 1 · 2026-03-25 07:46:24

217

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Let $A$ be a set of $n$ residues $\pmod{n^{2}}$. Prove that there exists a set $B$ of of $n$ residues $\pmod{n^{2}}$ ...

Published on 25 Mar 2026 - 7:46

score 216 · Answer 2 · 2019-09-08 09:09:25

216

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How to solve this problem that appears in Imo 1982

Published on 08 Sep 2019 - 9:09

score 58 · Answer 3 · 2026-03-29 18:32:53

58

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Distribution of items among two people, from PSS by Arthur Engel.

Published on 29 Mar 2026 - 18:32

score 379 · Answer 4 · 2019-09-09 03:36:13

379

Views

Find number of ways to select subset with distinct objects of at most K size.

Published on 09 Sep 2019 - 3:36

score 120 · Answer 5 · 2019-09-09 07:54:00

120

Views

There are 10 teams. Each will fought every other exactly once, each team will have exactly 9 matches.

Published on 09 Sep 2019 - 7:54

score 114 · Answer 6 · 2026-03-26 23:05:51

114

Views

Does a strictly increasing function satisfying this exist?

Published on 26 Mar 2026 - 23:05

score 126 · Answer 7 · 2019-09-09 13:48:54

126

Views

Power of Complex Numbers in Contest Geometry

Published on 09 Sep 2019 - 13:48

score 585 · Answer 8 · 2026-03-29 17:27:34

585

Views

Proof that each of the three cevians is divided in the ratio $1:3:3$

Published on 29 Mar 2026 - 17:27

score 189 · Answer 9 · 2019-09-11 01:16:40

189

Views

Mock AMC 10 from AoPS

Published on 11 Sep 2019 - 1:16

score 92 · Answer 10 · 2019-09-11 13:42:01

92

Views

Construct $n$ black and red circles

Published on 11 Sep 2019 - 13:42

score 90 · Answer 11 · 2026-03-25 11:21:23

90

Views

Olympiad Inequality $\frac{ab+bc+ca}{a+b+c}(\sum_{cyc}\frac{1}{2a+b})\leq 1$ with proof (long post)

Published on 25 Mar 2026 - 11:21

score 243 · Answer 12 · 2026-03-25 11:19:18

243

Views

Prove this inequality via weighted Jensen inequality

Published on 25 Mar 2026 - 11:19

score 271 · Answer 13 · 2019-09-13 01:54:18

271

Views

Proof Verification on Putnam Exam Problem

Published on 13 Sep 2019 - 1:54

score 137 · Answer 14 · 2026-03-25 09:43:07

137

Views

$ \frac{x_1}{1+x_1^2} + \frac{x_2}{1+x_1^2+x_2^2} +...+\frac{x_n}{1+x_1^2+x_2^2+...x_n^2} \le \sqrt{n}$ for $x_i > 0$

Published on 25 Mar 2026 - 9:43

score 231 · Answer 15 · 2026-03-29 02:11:11

231

Views

Train stops at $n$ stations

Published on 29 Mar 2026 - 2:11

List Question

Let $A$ be a set of $n$ residues $\pmod{n^{2}}$. Prove that there exists a set $B$ of of $n$ residues $\pmod{n^{2}}$ ...

How to solve this problem that appears in Imo 1982

Distribution of items among two people, from PSS by Arthur Engel.

Find number of ways to select subset with distinct objects of at most K size.

There are 10 teams. Each will fought every other exactly once, each team will have exactly 9 matches.

Does a strictly increasing function satisfying this exist?

Power of Complex Numbers in Contest Geometry

Proof that each of the three cevians is divided in the ratio $1:3:3$

Mock AMC 10 from AoPS

Construct $n$ black and red circles

Olympiad Inequality $\frac{ab+bc+ca}{a+b+c}(\sum_{cyc}\frac{1}{2a+b})\leq 1$ with proof (long post)

Prove this inequality via weighted Jensen inequality

Proof Verification on Putnam Exam Problem

$ \frac{x_1}{1+x_1^2} + \frac{x_2}{1+x_1^2+x_2^2} +...+\frac{x_n}{1+x_1^2+x_2^2+...x_n^2} \le \sqrt{n}$ for $x_i > 0$

Train stops at $n$ stations

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