Search found 33 matches

by kfoozminus
Mon Jun 10, 2013 10:22 pm
Forum: Combinatorics
Topic: Couples in a Row
Replies: 1
Views: 1674

Couples in a Row

In how many ways $4$ couples can stand in a row so that no one doesn't stand beside it's pair?
by kfoozminus
Tue Jan 29, 2013 12:55 am
Forum: Social Lounge
Topic: info.
Replies: 4
Views: 2541

Re: info.

nafistiham wrote:আপু, তাই কি ? এইটা তো প্রাইমারীতে যে সেকেন্ড হয়, তাকে দেওয়া হয় বলে জানি ।
স্যরি, আমি এখনো আগের যুগে পইড়া আছি, খুব সম্ভবত আগে এইভাবে দেওয়া হত... মানে এই ঘোষণাটা আসার আগে http://www.matholympiad.org.bd/blog/?p=292
by kfoozminus
Mon Jan 28, 2013 11:06 pm
Forum: Social Lounge
Topic: info.
Replies: 4
Views: 2541

Re: info.

আর 'সজল-কাজল স্মৃতি পুরষ্কার' দেওয়া হয় জাতীয় উৎসবে অংশগ্রহণকারী বয়সে সবচে' ছোট প্রতিযোগীকে... :)
by kfoozminus
Tue Jan 22, 2013 6:45 pm
Forum: Divisional Math Olympiad
Topic: Some problems of last year divisionals, I need help for
Replies: 36
Views: 12074

Re: Some problems of last year divisionals, I need hel for

nafistiham wrote:
Suppose, "Probability of opened door $A$"= $P_{A}$
then the probability will be $P_A \cdot (P_B+P_C+P_D \cdot P_E)$
first, i tried it same way too, but it gives 1.2 as answer!
but, i'm not sure about sourav's solution too... :|
by kfoozminus
Wed Jan 16, 2013 12:50 am
Forum: Number Theory
Topic: 9TH DIGIT PALINDROMIC
Replies: 4
Views: 2011

Re: 9TH DIGIT PALINDROMIC

nafistiham wrote:
the smallest $3$ $9$ digit palindrome are $100000001,100010001,100020001$
first $2$ are not squares.So....
[Actually, I wondered, how it is the smallest. So, shared my observation.]
$9999^2$ is a $8$ digit number, $10000^2$ isn't palindromic, so... :)
by kfoozminus
Mon Jan 14, 2013 10:55 pm
Forum: Number Theory
Topic: 9TH DIGIT PALINDROMIC
Replies: 4
Views: 2011

Re: 9TH DIGIT PALINDROMIC

$10001^2=100020001$ :)
by kfoozminus
Mon Jan 14, 2013 10:44 pm
Forum: Secondary Level
Topic: cyclic combi
Replies: 1
Views: 2927

Re: cyclic combi

একটি মুক্তোকে স্থির রেখে বাকি $n-1$ সংখ্যক মুক্তোকে $(n-1)!$ ভাবে সাজানো যাবে। যেহেতু মালাকে ওল্টালে একই বিন্যাস পাওয়া যায়, সুতরাং বিন্যাস সংখ্যা হবে $\frac{(n-1)!}{2}$, আবার $r$ সংখ্যক একই মুক্তো আছে, সুতরাং - $\dfrac{(n-1)!}{2\cdot r!}$
by kfoozminus
Mon Jan 14, 2013 1:32 am
Forum: Computer Science
Topic: IDE
Replies: 26
Views: 18530

Re: IDE

code::blocks, still! ;)
by kfoozminus
Mon Jan 07, 2013 1:22 pm
Forum: Combinatorics
Topic: Help please
Replies: 1
Views: 1434

Re: Help please

first permute $m-1$ dogs keeping fixed $1$ dog, and then permute $n$ cats among $m$ blank seats between the dogs.
$(m-1)!\cdot ^mP_n$
by kfoozminus
Mon Jan 07, 2013 1:07 pm
Forum: Secondary Level
Topic: Multiple of 5
Replies: 8
Views: 2996

Re: Multiple of 5

simple logic: starting with $10000000$, we get $10$ consecutive number as the 'sum of digits' for every $10$ numbers($10000000-10000009$, $10000010-10000019$, ...) and there're two 'multiple of $5$' among any $10$ consecutive numbers.