Search found 185 matches
- Mon Jan 25, 2016 8:54 pm
- Forum: Social Lounge
- Topic: A frequently asked question (FAQ)
- Replies: 3
- Views: 3889
Re: A frequently asked question (FAQ)
Of course. But set square is not allowed in IMO.
- Sun Jan 10, 2016 10:40 pm
- Forum: Geometry
- Topic: Chinese Girls' Mathematical Olympiad 2015,P1
- Replies: 4
- Views: 4032
- Thu Aug 27, 2015 9:53 pm
- Forum: National Math Camp
- Topic: Exam 2, Online Number Theory Camp, 2015
- Replies: 24
- Views: 21884
Re: Exam 2, Online Number Theory Camp, 2015
এখনো শুরু হয় না ক্যারে???
- Fri Feb 20, 2015 12:37 am
- Forum: Combinatorics
- Topic: Iran 3rd round 2013
- Replies: 4
- Views: 3847
Re: Iran 3rd round 2013
I got the same result. Use this
$(a_{1}^2+\cdots+a_{n}^2)(1+\cdots+1)\geq (a_{1}+\cdots+a_{n})^2$
$(a_{1}^2+\cdots+a_{n}^2)(1+\cdots+1)\geq (a_{1}+\cdots+a_{n})^2$
- Wed Feb 18, 2015 2:00 pm
- Forum: Combinatorics
- Topic: Iran 3rd round 2013
- Replies: 4
- Views: 3847
Re: Iran 3rd round 2013
How to apply Jensen? Please explain. I think Cauchy Schwarz does the work.
- Mon Feb 16, 2015 12:56 am
- Forum: Combinatorics
- Topic: Iran 3rd round 2013
- Replies: 4
- Views: 3847
Iran 3rd round 2013
What is the maximal number of rooks can be placed on a $n\times n$ so that every rook is threatened by at most $2k$ rooks where $k$ is a given positive integer ?
- Tue Jan 20, 2015 1:50 pm
- Forum: Combinatorics
- Topic: n+1 rows and columns
- Replies: 10
- Views: 8035
Re: n+1 rows and columns
Please,explain this part.Nirjhor wrote:I
Now the hypothesis, in language of our mapping, is that we can never achieve an injective map $f:\mathcal A\mapsto \mathcal B$ by removing some segments from the original map.
- Thu Jan 15, 2015 4:56 pm
- Forum: Combinatorics
- Topic: n+1 rows and columns
- Replies: 10
- Views: 8035
Re: n+1 rows and columns
Actually I wanted to count the number of black cells we need "at least" & present them as the intersections so that i can prove there "always" exists $i$ rows & $j$ columns with given condition. I think you misunderstood the problem.You have to prove that there exist $i$ rows and $j$ columns with $...
- Tue Jan 13, 2015 12:22 am
- Forum: Combinatorics
- Topic: n+1 rows and columns
- Replies: 10
- Views: 8035
Re: n+1 rows and columns
WHY??Samiun Fateeha Ira wrote:We want to colour the least possible cells in black so that all the $n!$ sets may have at least one black cell.
- Tue Jan 06, 2015 12:32 pm
- Forum: Combinatorics
- Topic: n+1 rows and columns
- Replies: 10
- Views: 8035
Re: n+1 rows and columns
If a set of $n$ cells have the property that no $2$ cells are on the same row or column,then the set contains at least one black cell.