Search found 172 matches

by Zzzz
Mon Jan 31, 2011 9:48 am
Forum: H. Secondary: Solved
Topic: Dhaka Higher Secondary 2011/3
Replies: 16
Views: 6720

Re: Dhaka Higher Secondary 2011/3

whats the problem with my sollution bro...?:o You wrote $P(A)=\{\Phi, emptyset\}$ Its wrong. Simply think, if $A=\{a\}$ what would be its power set? the $P(A)$ would be $\{\{a\},\Phi\}$ right? Here $a$ is the only element of $A$. In our main problem $\Phi$ was also only element of $A$, so we should...
by Zzzz
Sun Jan 30, 2011 11:30 am
Forum: Secondary Level
Topic: Largest value of (x+y)
Replies: 4
Views: 2031

Re: Largest value of (x+y)

$x,y \in \mathbb N$
by Zzzz
Sun Jan 30, 2011 7:31 am
Forum: H. Secondary: Solved
Topic: Dhaka Higher Secondary 2011/3
Replies: 16
Views: 6720

Re: Dhaka Higher Secondary 2011/3

Hey . $\Phi $ is a set. $A=\{\Phi\}$ is not an empty set. It has an element which is $\Phi$. If they said $A=\Phi$ then we could say $A$ is an empty set.
by Zzzz
Sun Jan 30, 2011 7:28 am
Forum: Secondary: Solved
Topic: Dhaka Secondary 2011/1 (Higher Secondary 2011/1)
Replies: 9
Views: 8042

Re: Dhaka Secondary 2011/1 (Higher Secondary 2011/1)

The answer isn't the one Tahmid posted,it is as follows- The answer is 76. Here we must know that in the silver ring set,there are 12 kinds,and in the gold ring set,there are 10 kinds.So at least 2 kinds of silver ring is different from the gold kinds.Now if we pick up 75 rings , all of them can be...
by Zzzz
Sat Jan 29, 2011 9:33 pm
Forum: Secondary Level
Topic: Largest value of (x+y)
Replies: 4
Views: 2031

Largest value of (x+y)

$x,y \in \mathbb N$. Find the largest value of $(x+y)$ such that \[20x+11y=2011\]
made by Sakal Roy- Khulna Math Club
by Zzzz
Sat Jan 29, 2011 2:28 pm
Forum: Secondary: Solved
Topic: Dhaka Secondary (Higher Secondary) 2011/5
Replies: 9
Views: 4375

Re: Dhaka Secondary (Higher Secondary) 2011/5

Please write full solution so that someone can tell whether you are right or wrong or where is your fault...

*to hide something write : [ h i d e ] text [ / h i d e ] (without spaces)
by Zzzz
Sat Jan 29, 2011 11:44 am
Forum: H. Secondary: Solved
Topic: Dhaka Higher Secondary 2011/9
Replies: 11
Views: 10068

Re: Dhaka Higher Secondary 2011/9

Solution: Base $2$ representation of $1952$ is $11110100000$ So, $1952=2^{10}+2^9+2^8+2^7+2^5$ $\Rightarrow f(1952)=f(2^{10}+2^9+2^8+2^7+2^5)$ $=f(2^{10})+f(2^9)+f(2^8)+f(2^7)+f(2^5)$ As, $f(2^n)=f(2^{n+2})$, $f(2^{10})=f(2^8)=f(2^6)=f(2^4)=f(2^2)=f(2^0)$ Similarly $f(2^9)=f(2^7)=f(2^5)=...=f(2^1)$ ...
by Zzzz
Sat Jan 29, 2011 9:46 am
Forum: H. Secondary: Solved
Topic: Dhaka Higher Secondary 2011/9
Replies: 11
Views: 10068

Re: Dhaka Higher Secondary 2011/9

Is the first relation valid for $n =0$ and the second relation valid for all $X \subset \mathbb N\cup \{0\}$ ?

*edited
by Zzzz
Sat Jan 29, 2011 9:44 am
Forum: H. Secondary: Solved
Topic: Dhaka Higher Secondary 2011/3
Replies: 16
Views: 6720

Re: Dhaka Higher Secondary 2011/3

Ah.. guys are getting closer. One said $B=\Phi$, another said $B=\{\Phi\}$. What's next?

You should explain your answers ...
by Zzzz
Sat Jan 29, 2011 7:51 am
Forum: H. Secondary: Solved
Topic: Dhaka Higher Secondary 2011/3
Replies: 16
Views: 6720

Re: Dhaka Higher Secondary 2011/3

Hint:
A set can be element of a set ;)