## Dhaka Secondary 2011/10

Problem for Secondary Group from Divisional Mathematical Olympiad will be solved here.
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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.
BdMO
Posts: 134
Joined: Tue Jan 18, 2011 1:31 pm

### Dhaka Secondary 2011/10

For three non empty finite sets \$A, B, C\$ the following relations hold:
\$B \cap (C – A) = \{ \} \$
\$B \cap C \not = \{ \}\$
\$A,B,C \subset N\$ (\$N\$ is the set of natural numbers)
Given that \$A = \{1,2,3,4\}, C = \{3,4,5,6\}\$ and no element of \$B\$ is greater than the largest element of \$C\$ how many possible options are there for \$B\$?

leonardo shawon
Posts: 169
Joined: Sat Jan 01, 2011 4:59 pm
Location: Dhaka

### Re: Dhaka Secondary 2011/10

\$B \cap (C-A) = \{\}\$
\$B\cap {5,6} = \{\}\$
[value of (C-A) ]
so,, \$B\not = {5,6}\$ [not equal]
cause \$B\cap C \not =\{\}\$

so the possible value of B is {3,4}
\$B={3,4}\$
Ibtehaz Shawon
BRAC University.

long way to go .....

Avik Roy
Posts: 156
Joined: Tue Dec 07, 2010 2:07 am

### Re: Dhaka Secondary 2011/10

@Shawon, you have some problem with set theoretic notations, work on that.

You solution is close, think a bit more.
"Je le vois, mais je ne le crois pas!" - Georg Ferdinand Ludwig Philipp Cantor

Tahmid Hasan
Posts: 665
Joined: Thu Dec 09, 2010 5:34 pm

### Re: Dhaka Secondary 2011/10

বড় ভালবাসি তোমায়,মা