Search found 1175 matches

by *Mahi*
Sun Jan 30, 2011 9:26 am
Forum: Secondary: Solved
Topic: Dhaka Secondary 2011/7
Replies: 11
Views: 9062

Re: Dhaka Secondary 2011/7

I don't think so!
Here,the name aaa or bbb is allowed.
So,it will be much less than 20
by *Mahi*
Sat Jan 29, 2011 11:01 pm
Forum: Secondary: Solved
Topic: Dhaka Secondary 2011/9
Replies: 9
Views: 7703

Re: Dhaka Secondary 2011/9

This one is really tricky,here is how I tamed it- Solution: We know that $2\equiv -1(mod 3) \Rightarrow2^x\equiv (-1)^x(mod 3)$ So we can strike out the numbers divisible by $3$. Now again the numbers which 'survive' are always like this- $x^2\equiv 1 (mod 3)$ So we have to just sum up the first $20...
by *Mahi*
Sat Jan 29, 2011 10:49 pm
Forum: Secondary: Solved
Topic: Dhaka Secondary 2011/7
Replies: 11
Views: 9062

Re: Dhaka Secondary 2011/7

Solution:
As we know that using $n$ letters $3$ times when repetition is allowed ,at most $n^3$ different words can be formed.
So the big one needs $5$ letters as $5^3=125>120$
by *Mahi*
Sat Jan 29, 2011 10:43 pm
Forum: Secondary: Solved
Topic: Dhaka Secondary 2011/4
Replies: 2
Views: 2088

Re: Dhaka Secondary 2011/4

Let us number the equations i,ii,iii......serially .Now by subtracting ii from i we get
$b+d=-1/3$
and subtracting iii from i we get,
$c+e=-1/2$
Now the solution is straightforward,$a=11/6$
by *Mahi*
Sat Jan 29, 2011 10:32 pm
Forum: Secondary: Solved
Topic: Dhaka Secondary 2011/1 (Higher Secondary 2011/1)
Replies: 9
Views: 8102

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 ...