Rangpur Secondary 2011/9

Problem for Secondary Group from Divisional Mathematical Olympiad will be solved here.
Forum rules
Please don't post problems (by starting a topic) in the "Secondary: Solved" forum. This forum is only for showcasing the problems for the convenience of the users. You can post the problems in the main Divisional Math Olympiad forum. Later we shall move that topic with proper formatting, and post in the resource section.
User avatar
Moon
Site Admin
Posts: 751
Joined: Tue Nov 02, 2010 7:52 pm
Location: Dhaka, Bangladesh
Contact:

Rangpur Secondary 2011/9

Unread post by Moon » Wed Feb 02, 2011 6:50 pm

Problem 9:
At a convention, flags of $4$ countries are to be hoisted on $2$ poles so that no pole is left empty and all the flags get hoisted. More than one flag must not be placed at the same height of the same pole. Rather, they can be placed above or below an already placed flag. In this manner, more than one flag can be placed serially on a single pole. How many ways can the flags be hoisted?
"Inspiration is needed in geometry, just as much as in poetry." -- Aleksandr Pushkin

Please install LaTeX fonts in your PC for better looking equations,
learn how to write equations, and don't forget to read Forum Guide and Rules.

User avatar
Tahmid Hasan
Posts: 665
Joined: Thu Dec 09, 2010 5:34 pm
Location: Khulna,Bangladesh.

Re: Rangpur Secondary 2011/9

Unread post by Tahmid Hasan » Wed Feb 02, 2011 8:05 pm

the possible cases are 2 flags o each pole,3 on first and3 on 2nd.
in each of the cases the flags can be hoisted in $4!$ ways. so the ans is $4!*3=72$
বড় ভালবাসি তোমায়,মা

Post Reply