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Old High School Olympiads Regional, National, and International Math Olympiads before 2001 mostly, recent years have been posted in order to make contest collections richer
Regional, National, and International Math Olympiads before 2001 mostly, recent years have been posted in order to make contest collections richer
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Old High School Olympiads Regional, National, and International Math Olympiads before 2001 mostly, recent years have been posted in order to make contest collections richer
Regional, National, and International Math Olympiads before 2001 mostly, recent years have been posted in order to make contest collections richer
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k a April Highlights and 2025 AoPS Online Class Information
jlacosta   0
Apr 2, 2025
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0 replies
jlacosta
Apr 2, 2025
0 replies
J
H
k i testing latex post , please ignore
parmenides51   3
N Feb 23, 2025 by parmenides51
Source: used with https://artofproblemsolving.com/community/c3170239_latex_testing_for_post_collections
issue 1 ..,
Click to reveal hidden text
3 replies
parmenides51
Oct 10, 2022
parmenides51
Feb 23, 2025
J
H
i Geo Collections + Forums + Greek Aops Index
parmenides51   57
N Oct 12, 2024 by parmenides51
In order to keep an eye to any contest collection that I have created and is not in aops contest collections, I created a collection with all that in a link: Geo Collections + Forums + Greek Aops Index

It contains so far (in these categories):

$\bullet$ Forums
$\bullet \bullet$ Geometry Mathley
$\bullet \bullet$ Old High School Olympiads
$\bullet \bullet$ Old Russian Math Olympiads

All geometry mentioned below in one forum collection:
$\bullet \bullet$ Geometry Collections and Contests

$\bullet$ Aops Geo Mocks
$\bullet$ Aops Mock Contests - Geometry


$\bullet \bullet$ geo national (geometry from:)
$\bullet$ Argentina NMO (Round 2-4, Finals, Provincial, Regional Round 2)
$\bullet$ Armenia NMO (outside aops)
$\bullet$ Belarus NMO VIII (outside aops)
$\bullet$ Belarus NMO IX (>>)
$\bullet$ Belarus NMO X (>>)
$\bullet$ Belarus NMO XI (>>)
$\bullet$ Belgium Flanders Juniors JWO (outside aops)
$\bullet$ Belgium Flanders Seniors VWO (>>)
$\bullet$ Belgium OMB Juniors (outside aops)
$\bullet$ Belgium OMB Seniors (>>)
$\bullet$ Brazil NMO (Round 2 + Finals)
$\bullet$ Bulgaria NMO Plane Geometry (outside aops)
$\bullet$ Bulgaria NMO 3D Geometry (>>)
$\bullet$ Costa Rica NMO (OLCOMA)
$\bullet$ Croatia MO (outside aops)
$\bullet$ Chile NMO (outside aops)
$\bullet$ Denmark MO (Mohr Contest) (outside aops)
$\bullet$ Estonia Open Junior MO (outside aops)
$\bullet$ Estonia Open Senior MO (>>)
$\bullet$ Greece JMO (outside aops)
$\bullet$ Greece NMO (outside aops)
$\bullet$ Hungary OKTV I (outside aops)
$\bullet$ Hungary OKTV II (>>)
$\bullet$ Hungary OKTV III (>>)
$\bullet$ Iceland NMO (outside aops)
$\bullet$ Indonesia MO Province OSP SMA (outside aops)
$\bullet$ Kazakhstan NMO IX (outside aops)
$\bullet$ Kazakhstan NMO X (>>)
$\bullet$ Kazakhstan NMO XI (>>)
$\bullet$ Lithuania juniors (outside aops)
$\bullet$ Mexico NMO (States Semifinals + Finals, Finals)
$\bullet$ Moldova NMO VII-VIII (outside aops)
$\bullet$ Moldova NMO IX-XII Plane Geometry (>>)
$\bullet$ Moldova NMO 3D Geometry (>>)
$\bullet$ New Zealand MO (outside aops)
$\bullet$ Paraguay NMO (OMAPA) (outside aops)
$\bullet$ Peru NMO (ONEM) (Rounds 2-3, Finals)
$\bullet$ Poland Juniors , Round 1+2 (outside aops)
$\bullet$ Poland Juniors, Finals (>>)
$\bullet$ Portugal NMO (outside aops)
$\bullet$ Romania District 3D Geometry (outside aops)
$\bullet$ Romania District Plane Geometry (>>)
$\bullet$ Romania NMO 3D Geometry (outside aops)
$\bullet $ Romania NMO Plane Geometry (>>)
$\bullet$ Swiss NMO (outside aops)
$\bullet$ Ukraine NMO VIII (outside aops)
$\bullet$ Ukraine NMO IX (>>)
$\bullet $ Ukraine NMO X-XI Plane Geometry (>>)
$\bullet$ Ukraine NMO 3D Geometry (>>)


$\bullet \bullet$ geo TST (geometry from:)
$\bullet$ Argentina Cono Sur TST (outside aops)
$\bullet$ Argentina Ibero TST (>>)
$\bullet$ Argentina IMO TST (>>)
$\bullet$ Argentina Training Lists Cono Sur (outside aops)
$\bullet$ Argentina Training Lists IberoAmerican (>>)
$\bullet$ Argentina Training Lists Rioplatense (>>)
$\bullet$ Bangladesh TST and Camp
$\bullet$ Belarus TST (outside aops)
$\bullet$ Brazil Training List Cono Sur 1999 - 2010 (outside aops)
$\bullet$ Brazil Training List Cono Sur 2011-20 (>>)
$\bullet$ Brazil Cono Sur TST (outside aops)
$\bullet$ Brazil IMO IberoAmerican TST (>>)
$\bullet$ Chile TST (outside aops)
$\bullet$ Croatia TST (outside aops)
$\bullet$ Cyprus TST (outside aops)
$\bullet$ Ecuador TST (outside aops)
$\bullet$ France TST (outside aops)
$\bullet$ Hong Kong TST (outside aops)
$\bullet$ Indonesia TST (outside aops)
$\bullet$ Italy TST (outside aops)
$\bullet$ Lithuania TST (outside aops)
$\bullet$ Peru Cono Sur TST (outside aops)
$\bullet$ Peru IberoAmerican TST (>>)
$\bullet$ Peru IMO TST (>>)
$\bullet$ Puerto Rico TST (outside aops)
$\bullet$ Serbia IMO TST (outside aops)
$\bullet$ Singapore TST (outside aops)
$\bullet$ Switzerland TST (outside aops)
$\bullet$ Taiwan TST (outside aops)
$\bullet$ Thailand TST (outside aops)
$\bullet$ Ukraine TST (outside aops)


$\bullet \bullet$ geo regional (geometry from:)
$\bullet$ 239 MO (St.Petersburg's Lyceum) (outside aops)
$\bullet$ Alberta High School Mathematics Competition (Canada) (outside aops)
$\bullet$ AESC MSU Internet Olympiad (Russia) (outside aops)
$\bullet$ All-Siberian Olympiad Finals (Russia) (outside aops)
$\bullet$ All-Siberian Olympiad Correspondence (Russia) (>>)
$\bullet$ All-Siberian Olympiad Qualifying (Russia) (>>)
$\bullet$ Almaty City MO (Kazakhstan) (outside aops)
$\bullet$ Association Mathematical Quebec Competition (Canada) (outside aops)
$\bullet$ Auckland MO (New Zealand) (outside aops)
$\bullet$ Champions Tournament (Ukraine) (Турнір чемпіонів) (outside aops)
$\bullet$ Clock-Tower School Junior (Romania) (outside aops)
$\bullet$ COMATEQ (Puerto Rico) (outside aops)
$\bullet$ Cordoba pre TSTs (Argentina) (outside aops)
$\bullet$ Dürer Math Competition (Hungary) (outside aops)
$\bullet$ El Número de Oro Certamen (Argentina) (outside aops)
$\bullet$ Euler Olympiad Remote (Russia) (outside aops)
$\bullet$ Euler Olympiad Regional & Final (Russia) (>>)
$\bullet$ Euler Teachers' MO (Russia) (outside aops)
$\bullet$ European Math Tournament (Belarus) (outside aops)
$\bullet$ Formula of Unity / Third Millennium Olympiad (Russia) (outside aops)
$\bullet$ HSGS Class 9 Contest (Vietnam) (outside aops)
$\bullet$ High Standards Olympiad (Russia) (Высшая проба) (outside aops)
$\bullet$ Innopolis University Open MO (Russia) (outside aops)
$\bullet$ Izumrud Olympiad Emerald by UrFU (Russia) (outside aops)
$\bullet$ Kharkiv City MO (Ukraine) (outside aops)
$\bullet$ Kharkiv Lyceum No 27 Olympiad (Ukraine) (outside aops)
$\bullet$ Kharkiv Masters Tournament (Ukraine) (outside aops)
$\bullet$ Kolomogorov Cup / Tournament (Russia)
$\bullet$ Kukin MO by OmSU (Russia) (outside aops)
$\bullet$ Kurchatov Olympiad (Russia) (outside aops)
$\bullet$ Kyiv City MO 1984-93 (Ukraine) (outside aops)
$\bullet$ Kyiv City MO 2003+ Round 1 (Ukraine) (>>)
$\bullet$ Kyiv City MO 2010+ Round 2 (Ukraine) (>>)
$\bullet$ Kyiv TST 2005-16 (for Ukraine MO) (outside aops)
$\bullet$ Kyiv TST 2017+ (for Ukraine MO) (>>)
$\bullet$ League of Winners Tournament (Russia) (outside aops)
$\bullet$ Lomonosov Tournament (Russia) (outside aops)
$\bullet$ Mathematical Multiathlon Tournament Juniors (Russia) (outside aops)
$\bullet$ Mathematical Multiathlon Tournament Seniors (Russia) (>>)
$\bullet$ Maths Beyond Limits Camp (Poland) (outside aops)
$\bullet$ May Olympiad, level 1 (Latin America) (outside aops)
$\bullet $ May Olympiad, level 2 (Latin America) (>>)
$\bullet$ Minsk City Internet Olympiad (Junior) (Belarus) (outside aops)
$\bullet$ MIPT Metropolitan Olympiad (Russia) (outside aops)
$\bullet$ Moscow Corespondence Competition 6-8 MO (Russia) (outside aops)
$\bullet$ Moscow Teachers' MO (Russia) (outside aops)
$\bullet$ OMAFOROS - OFO,FOFO, COFFEE (Argentina) (outside aops)
$\bullet$ Oral Moscow City MO VI-VII (Russia) (outside aops)
$\bullet$ Oral Moscow City Team MO 1999 - 2004 (Russia) (outside aops)
$\bullet$ Oral Moscow City Team MO 2005-19 (Russia) (>>)
$\bullet$ Oral Moscow City Team MO 2020+ (Russia) (>>)
$\bullet$ Rio de Janeiro MO (OMERJ) (Brazil) (outside aops)
$\bullet$ Rioplatense Olympiad, level 1 (Latin America) (outside aops)
$\bullet$ Rioplatense Olympiad, level 2 (Latin America) (>>)
$\bullet$ Rioplatense Olympiad, level 3 (Latin America) (>>)
$\bullet$ Rusanovsky Lyceum, Kyiv Olympiad(Ukraine) (outside aops)
$\bullet$ Savin Competition 1990 - 2015 (Russia) (outside aops)
$\bullet$ Savin Competition 2016+ (Russia) (>>)
$\bullet$ Savin Tournament (Russia) (>>)$\bullet$ SPBU School Olympiad besides Finals X-XI (Russia) (outside aops)
$\bullet$ SPBU School Olympiad, Finals X-XI - plane geometry (Russia) (>>)
$\bullet$ SPBU School Olympiad, Finals X-XI - 3D geometry (Russia) (>>)
$\bullet$ Ukraine Correspodence MO (outside aops)
$\bullet$ Ukrainian From Tasks to Tasks (outside aops)
$\bullet$ Ukrainian Tournament of Young Mathematicians Qualifying (outside aops)
$\bullet$ Ukrainian Tournament of Young Mathematicians Finals (>>)
$\bullet$ UNSW School Mathematics Competition Juniors (Australia) (outside aops)
$\bullet$ UNSW School Mathematics Competition Seniors (Australia) (>>)
$\bullet$ UQ/QAMT Problem Solving Competition (Australia) (outside aops)
$\bullet$ VU MIF Olympiad - geometry (Lithuania) (outside aops)
$\bullet$ Youth Mathematical School Olympiad ordinary (Russia) (outside aops)
$\bullet$ Youth Mathematical School Olympiad research (Russia) (>>)
$\bullet$ Zhautykov City Olympiad - geometry (Kazakstan) (outside aops)


$\bullet \bullet$ geo USA (geometry from:)
$\bullet$ BMT / Geometry Rounds
$\bullet$ BMT / Geometry problems from non Geometry Rounds
$\bullet$ CMIMC / Geometry Rounds
$\bullet$ CMIMC / Geometry problems from non Geometry Rounds
$\bullet$ HMMT / Geometry Rounds 2014-21
$\bullet$ PUMaC / Geometry Rounds 2006-14
$\bullet$ PUMaC / Geometry Rounds 2005-20
$\bullet$ PUMaC / Geometry problems from non Geometry Round


$\bullet \bullet$ geo olympiads
$\bullet$ Adygea Teachers' Geometry Olympiad (outside aops)
$\bullet$ Cabri Clubs (outside aops)
$\bullet$ Iranian Geometry Olympiad (outside aops)
$\bullet$ Mexican Geometry Olympiad (outside aops)
$\bullet$ Novosibirsk Oral Olympiad in Geometry (outside aops)
$\bullet$ Oral Moscow Geometry Olympiad (outside aops)
$\bullet$ Sharygin Geometry Olympiad (outside aops)
$\bullet$ Yaskinsky Geometry Olympiad (outside aops)
$\bullet$ Ukrainian Geometry Olympiad (outside aops)
$\bullet \bullet$ geometry olympiads not yet in contest collections


$\bullet \bullet$ geo shortlists (not IMO, BMO, JBMO, ELMO)
$\bullet$ Baltic Way Shortlist 2009-16 (outside aops)
$\bullet$ Baltic Way Shortlist 2017+ (outside aops)
$\bullet$ CentroAmerican Shortlist (outside aops)
$\bullet$ Cono Sur Olympiad Shortlist (outside aops)
$\bullet$ IberoAmerican Shortlist 1992 - 2010 (outside aops)
$\bullet$ IberoAmerican Shortlist 2011+ (>>)
$\bullet$ Indonesia Shortlist (INAMO OSN) (outside aops)
$\bullet$ IMOC Shortlist (Taiwan) (outside aops)
$\bullet$ Real IMO Shortlist (International Monster's Olympiad) (outside aops)
$\bullet$ Romanian Master in Mathematics Shortlist (outside aops)
$\bullet$ Thailand MO Shortlist (outside aops)


$\bullet \bullet$ geo IMO Longlists (outside aops)
$\bullet$ IMO Longlist I 1966-70 Geometry
$\bullet$ IMO Longlist II 1971-76 Geometry
$\bullet$ IMO Longlist III 1977-82 Geometry
$\bullet$ IMO Longlist IV 1983-85 Geometry
$\bullet$ IMO Longlist V 1986-88 Geometry
$\bullet$ IMO Longlist VI 1989-82 Geometry


$\bullet \bullet$ geo magazines
$\bullet$ Mathematical Excalibur - geometry (outside aops)
$\bullet$ Mathematical Reflections Junior - geometry (outside aops)
$\bullet$ Mathematical Reflections Senior - geometry (>>)
$\bullet$ Mathematical Reflections Olympiad - geometry (>>)
$\bullet$ Mathematical Reflections Undergraduate - geometry (>>)
$\bullet$ Quantum English - geometry (outside aops)
$\bullet$ Romanian Mathematical Magazine (outside aops)
$\bullet$ U sviti matematyky , part 1- geometry (In the World of Mathematics) (outside aops)
$\bullet$ U sviti matematyky , part 2 - geometry (In the World of Mathematics) (>>)


Akopyan's Geometry in Figures (random problems posted in aops)

$\bullet \bullet$ Greek Aops Index
$\bullet$ Greek Aops Index - Άλγεβρα
$\bullet$ Greek Aops Index - Ανισότητες
$\bullet$ Greek Aops Index - Γεωμετρία
$\bullet$ Greek Aops Index - Θεωρία Αριθμών
$\bullet$ Greek Aops Index - Συνδυαστική

PS.1. The links outside aops link to my blogspot page, in each competition's tab, imogeometry.blogspot.com.

PS.2. The geometry problems I have solved inside aops are collected here.
57 replies
parmenides51
Mar 7, 2020
parmenides51
Oct 12, 2024
J
H
i Forum's Purpose - Index of posted Contest Collections
parmenides51   29
N Mar 30, 2023 by huashiliao2020
I created this forum in order to post High School Math Olympiads before 2001 (not present in aops at the moment) in order to add more Contests to the existing Aops Contest Collections (without spamming the existing forums by posting too many posts in so little time). I also post recent problems not available at the moment at contest collections, in oder to create those post collections.
Anyone is welcome to post problems from a national competition (final round or TST) of his / her country not already posted in Aops Contest Collections, to get those links (just not post random problem but all from each year's competition). There is no limit to how many problems anyone may post in this forum, as it serves as a new problem collection source for more (older usually) posts collection (e.g. anyone may post in a day 40 different problems from 10 years of his \ her 4 problem's olympiad in 40 different posts - one problem at each post).

Forum Contests Collected:
- Mathcenter Contest (Thai)
- Mathlinks Contests (old name of aops)
- OIFMAT (FMAT - Chilean)
- Oliforum Contest (Italian)
- VMEO (VMF - Vietnamese)


Below are the contest collections I have created using this forum :
- Arab Math Olympiad
- Argentina NMO Finals: 2008
- Argentina NMO Round 4 / Regional Geo, L1, L2, L3, years 1995-2022
- Argentina Provincional Geo: L1, L2, L3 , 1995-2022
- Argentina TST / geometry : Ibero , IMO, Cono Sur
- Austrian - Polish Competition : 1979-2000
- Austria Beginners' Competition: 2001-08
- Belarus National MO: 1995, 1997 missing problems , 1998 , 2001, 2002, 2003,2006 , 2014
- Belarus TST : 1998 , 2000 , 2009 , 2010, 2011, 2012, 2014, 2015, 2016
- Bosnia and Herzegovina JBMO TST: 2003-07
- Brazil TSTs: EGMO, Geometry : Cono Sur, Cono Sur Training List , ΙΜΟ + Ibero ,
- Brazil IMO TST: 2007-16
- Bulgaria National MO: 1993-96
- Chile Contests / Chile NMO 1989 -2015
- Czech and Slovak Olympiad III A: so far 1986, 1991- 2001
- Czech-Polish-Slovak Junior Match: all
- Croatia National MO: 1996-2004
- Croatia TST: so far 2001, 2002, 2003
- Estonia Open Junior: 2001-2005, 2006, 2007, 2008-2019
- Estonia Open Senior: 2001-2005, 2006, 2007, 2008-2019
- Estonia National MO: so far 1996-2007, (soon 2008-2021)
- Estonia TST: 1992-95, 1998-2000, 2001-19
- French National MO: 1986, 1988-2003
- Final Mathematical Cup
- Germany / Bundeswettbewerb Mathematik : 1974-1982 , 1990
- Germany / National MO: so far 1965, 1996- 2001, 2009
- Germany / QUEDMO (11 /15 editions so far)
- Greece Junior: 1996 - 2020
- Hungary / Kürschák: 1947-84
- Hungary / Dürer / Finals: 2019-21
- India / LIMIT : 2020
- India / Postal Coaching: 2007-09 , 2012
- Israel / National (Gillis) : 1995-98
- Israel / Grosman: so far 1995, 1997, 1999, 2001
- Italy TST: so far 1993-94, 1998
- Kyrgystan TST: 2010, 2018
- Lithuania / Grand Duchy of Lithuania 2009-20
- Macedonia North National MO: so far 1994, 1995, 1996, 1997, 1998, 1999, 2002, 2003, 2004, 2005
- May Olympiad all
- Moldova Contests /JBMO TST: 1999- 2020
- Moldova National MO
- Mongolia National MO: 1999-2002, 2007
- Netherlands / Dutch ΙΜΟ TST: 2021
- New Zealand / NZMOC Camp Selection Problems, New Zealand MO
- Norway / Abels Math Contest (Final Round): 1993- 2006
- Polish MO Finals: 1966-84
- Rioplatense L3 1990-99
- Romania MOP: ROMOP 2011 Juniors
- Romania JBMO TST : 2002-19
- Romania TST: so far 1989, 1990 , 1991 (missing), 1992, 1993, 1995
- Saudi Arabia / BMO TST: 2010-11, 2013, 2015-19
/ GMO TST: 2013-16, 2018
/ IMO TST: 2011.2013, 2015-19
/ Pre-TST + Training Tests: 2010-11, 2021
- Saudi Arabia JBMO TST: 2017, 2019
- Serbia National MO: 1974 - 2006 (also known as Yugoslavia before 1990)
- Serbia TST:
- Singapore Junior : 2006-2019 collected
- Singapore Open: 1995 - 2004, 2014, 2016-17
- Singapore Senior : 1996 - 2008, 2011-13, 2015-19,
- Singapore TST: 1995 -2003
- Slovenia National MO: 1997-2001, 2005
- Slovenia TST: so far 1997, 1998, 2005
- Soros Olympiad
- Spanish MO: 1966-83
- Sweden National MO: 1961 - 2020
- Switzerland TST : so far 1997 - 2004, 2015 .
- Thailand MO: 2004- 15
- Ukraine National MO: 1997, 1998, 1999, 2005
- Ukraine TST: 1999, 2009-18
- USA / iΤest: 2005

Basic Source: Imomath

PS. My posting ability in public forums is as everyone’s else limited. Therefore when I post in public forums, I post only the geometry problems. When my source is written not in English, only the geometry ones are posted as I spend time translating them by google translate. When my source is written in English, I post the whole problem set in aops, posting the non-geometry problems in this forum and adding all the problems in contest collections.
In this forum’s index, anyone may find which contests’ years have been posted inside this forum.
In the future, each year's post collections shall be available in the Contests Collections, till then anyone may find them above.

Related forums:
Old Russian Math Olympiads
China High School Contests
KöMaL (Hungarian Magazine)

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PS.2 Test
29 replies
parmenides51
Feb 11, 2020
huashiliao2020
Mar 30, 2023
J
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x_1 + x_2 +...+ x_n = 16, 1/x_1 + 1/x_2 +...+ 1/x_n =1
parmenides51   2
N 5 minutes ago by lightsynth123
Source: Singapore Junior Math Olympiad 2012 2nd Round p4 SMO
Determine the values of the positive integer $n$ for which the following system of equations has a solution in positive integers $x_1, x_2,...,, x_n$. Find all solutions for each such $n$.
$$\begin{cases} x_1 + x_2 +...+ x_n = 16 \\ \\ \dfrac{1}{x_1} + \dfrac{1}{x_2} +...+ \dfrac{1}{x_n} = 1\end{cases}$$
2 replies
parmenides51
Mar 25, 2020
lightsynth123
5 minutes ago
J
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|a - b| is perfect square if a - b = a^2c - b^2d$ for consecutive c,d
parmenides51   1
N Yesterday at 1:34 PM by MuradSafarli
Source: 2011 Saudi Arabia IMO TST 2.1
Let $a$ and $b$ be integers such that $a - b = a^2c - b^2d$ for some consecutive integers $c$ and $d$. Prove that $|a - b|$ is a perfect square.
1 reply
parmenides51
Dec 29, 2021
MuradSafarli
Yesterday at 1:34 PM
J
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sum of k(3k+1 ) / {(3k-1)(3k+2) as irreducible fraction
parmenides51   2
N Yesterday at 12:43 PM by Wiley_H
Source: 2015 Argentina OMA Finals L3 p1
Express the sum of $99$ terms$$\frac{1\cdot 4}{2\cdot 5}+\frac{2\cdot 7}{5\cdot 8}+\ldots +\frac{k(3k+1 )}{(3k-1)(3k+2)}+\ldots +\frac{99\cdot 298}{296\cdot 299}$$as an irreducible fraction.
2 replies
parmenides51
Jan 16, 2023
Wiley_H
Yesterday at 12:43 PM
J
H
necklace of marbles of n inhabitants of an island, friends of enemies
parmenides51   2
N Yesterday at 10:10 AM by Bata325
Source: Norwegian Mathematical Olympiad 2004 - Abel Competition p4
Among the $n$ inhabitants of an island, where $n$ is even, every two are either friends or enemies. Some day, the chief of the island orders that each inhabitant (including himself) makes and wears a necklace consisting of marbles, in such a way that two necklaces have a marble of the same type if and only if their owners are friends.
(a) Show that the chief’s order can be achieved by using $n^2/4$ different types of stones.
(b) Prove that this is not necessarily true with less than $n^2/4$ types.
2 replies
parmenides51
Feb 11, 2020
Bata325
Yesterday at 10:10 AM
J
H
k^k +1 is divisible by 30
parmenides51   4
N Yesterday at 12:20 AM by lightsynth123
Source: Singapore Junior Math Olympiad 2015 2nd Round p5 SMO
Find all positive integers $k$ such that $k^k +1$ is divisible by $30$. Justify your answer.
4 replies
parmenides51
Mar 26, 2020
lightsynth123
Yesterday at 12:20 AM
J
H
xy >= ac + bd if x = \sqrt{a^2+b^2}, y = \sqrt{c^2+d^2},a,b,c,d> 0
parmenides51   4
N Wednesday at 1:13 PM by lightsynth123
Source: Singapore Junior Math Olympiad 2011 2nd Round p1 SMO
Suppose $a,b,c,d> 0$ and $x = \sqrt{a^2+b^2}, y = \sqrt{c^2+d^2}$. Prove that $xy \ge ac + bd$.
4 replies
parmenides51
Mar 26, 2020
lightsynth123
Wednesday at 1:13 PM
J
H
(2^a+1)/(2^b-1) is never an integer when a>b>2, positive integers
parmenides51   2
N Wednesday at 1:07 PM by lightsynth123
Source: Singapore Junior Math Olympiad 2013 2nd Round p4 SMO
Let $a,b,$ be positive integers and $a>b>2$. Prove that $\frac{2^a+1}{2^b-1}$ is never an integer
2 replies
parmenides51
Mar 26, 2020
lightsynth123
Wednesday at 1:07 PM
J
H
a\sqrt{b}=a+c, b\sqrt{c}=b+a, c\sqrt{a}=c+b , system
parmenides51   3
N Wednesday at 12:29 PM by lightsynth123
Source: Singapore Junior Math Olympiad 2014 2nd Round p4 SMO
Find, with justification, all positive real numbers $a,b,c$ satisfying the system of equations:
$$\begin{cases} a\sqrt{b}=a+c \\ b\sqrt{c}=b+a \\ c\sqrt{a}=c+b \end{cases}$$
3 replies
parmenides51
Mar 26, 2020
lightsynth123
Wednesday at 12:29 PM
J
H
tan 2x / tan x - 2 cot 2x / cot x=1
parmenides51   1
N Apr 15, 2025 by Mathzeus1024
Source: 1962-63 Germany R4 12.2
For which numbers $x$of the interval $0 < x <\pi$ holds:
$$\frac{\tan 2x}{\tan x} -\frac{2 \cot 2x}{\cot x}=1$$
1 reply
parmenides51
Oct 12, 2024
Mathzeus1024
Apr 15, 2025
J
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a f(x^n) + f(-x^n) = b
parmenides51   2
N Apr 14, 2025 by jasperE3
Source: 1967-68 Germany R4 12.3
Specify all functions $y = f(x)$, each in the largest possible domain (within the range of real numbers) of the equation
$$a \cdot f(x^n) + f(-x^n) = bx$$suffice, where $b$ is any real number, $n$ is any odd natural number and $a$ is a real number with $|a| \ne 1$.
2 replies
parmenides51
Oct 13, 2024
jasperE3
Apr 14, 2025
J
a