Riddles Options

[vivekpm]

15 calls?

Nopes. 15 is not minimum.

Cheers,

[shivani]

8 ??

[vivekpm]

8 ??

Correct...

Actually for any n >= 4, answer will be 2n-4. So in this case it is 8 indeed.

Cheers,

[shivani]

.. and if it is one way communication the answer would be 2n-2

(cheated.. this is the famous gossip problem in communication .. and Vikram.. not fair on your part to call it simple. Now I did nto understand the Call graph completely, so kindly explain. )

[vivekpm]

.. and if it is one way communication the answer would be 2n-2

(cheated.. this is the famous gossip problem in communication .. and Vikram.. not fair on your part to call it simple. Now I did nto understand the Call graph completely, so kindly explain. )

Firstly you got my name wrong

Yes this is a famous problem in communication and also in Discrete Mathematics. Here is the explanation in simple terms, as I understand.

Now take the case for 4 ladies. A,B,C,D.

In this case, A->D, B->C, A->B, C->D will result in all ladies having all information. So for n=4 number of calls are 4.

Now let us generalize this for any n > 4.

In this case, make two groups, one group containing 4 ladies and the other group containing n-4 ladies. Let these groups be called X and Y.

One lady from group X will call all the ladies in group Y. That is she will make n-4 calls. This lady now has all information except for the ladies in her group.
Now everyone in group X (group of 4) will exchange their information. This will take 4 calls as explained above. Everyone in group X, after this exercise will know all the gossips.
Now again, one lady from group X will call all the ladies in group Y. That is she will make n-4 calls resulting in everyone knowing all the information.

So the total is n-4+4+n-4 = 2n-4

Cheers,

[shivani]

Firstly you got my name wrong (IMG:style_emoticons/default/angry2.gif)

I am so sorry Vivek. I know all excuses are lame.. but my attention is elsewhere today .. shouldnt be online at all .

Apologies again.

[vivekpm]

Firstly you got my name wrong (IMG:style_emoticons/default/angry2.gif)

I am so sorry Vivek. I know all excuses are lame.. but my attention is elsewhere today .. shouldnt be online at all .

Apologies again.

Not a problem

Cheers,

[pranavjh]

Suhas.. stop fishing for compliments.

Vivek, I just present the problems here in hope that one of you would be able to solve them, and in the process I will learn. Please do not wait for my confirmation, and .. carry on..

Next one , since no one posted another..

"Travelling to a city, an old man lost his way. He came to a fork in the road and did not know which road to take. Standing at the fork were two men. Next to the men was a sign, which you may assume is correct, which stated that one of the two men always told the truth and one of the men always told lies (but it was not known which was which). The sign went on to say that travellers could only ask one of the men one question.
What question could the old man pose that would give him the information he needs to choose the correct route? "

Shivani, appreciate your efforts to post these questions. All of them have been a good learning experience for us.

And here is a possible solution to your problem.

Assuming I am the old man (which I am not ), I will ask following question to one of the two men. Assume that the two roads are named X and Y

I will ask following question to one of the person.

What will be the answer of the man standing next to you if I ask him "whether Y is the correct path for me?"

{
A = Men who tells the truth
B = Men who never tells the truth
}

1. Now if the person I asked the question is A, and if Y is correct path, he will say that other person will say "No" (because other person is B who is a liar and would have answered No because Y indeed is correct path, if I had asked him directly).

2. Now if the person I asked the question is B, and if Y is the correct path, he will say that other person will say "No" (because other person is A who always speaks the truth and he would have answered Yes if I had asked A directly).

3. If Y is incorrect, A will say that other person will say "yes".

4. If Y is incorrect, B will say that other person will say "yes".

So in both the cases, I will do exactly opposite to what the person answers me. So in cases 1 and 2 I will take Y (since the answer was NO) and in cases 3 and 4, I will take X (since answer was yes for Y)

Hope I have covered all the cases

Cheers,

I think there's another solution to this too. My question to either one of them would be,

"If I were to ask you which is the correct path, which one would you show me?"

With the same definition of A and B,

1) When I ask the question to A, he will point to the right path
2) When I ask the question to B, he would have showed me the wrong path, but since he has to lie, he will show me the right path.

So in either case, I follow the path that is pointed by the man I ask the question to.

Pranav

[shivani]

One of my level .. since no one else posted

You are competing in a race and overtake the runner in second place. Which position are in you now?

[august]

One of my level .. since no one else posted

You are competing in a race and overtake the runner in second place. Which position are in you now?

2nd

[shivani]

A different one.. A cryptogram : ).. lets see who gets this..

"Rit sdvry dmt ljagzhmrdjr. Ar'y cidr ritq dmt ztmvtaftk rh pt ridr ktrtmgajty rit vhlmyt hs tftjry."

Would just put a hint
r = t
i = h
t = e
s = f

[vivekpm]

"Rit sdvry dmt ljagzhmrdjr. Ar'y cidr ritq dmt ztmvtaftk rh pt ridr ktrtmgajty rit vhlmyt hs tftjry."

"The facts are unimportant. It's what they are perceived to be that determines the course of events."

Cheers,

[vivekpm]

Since Shivani is celebrating a "question-free week", let me take up the questioning mantle for a while

5 couples go out for dinner. And when they meet, they do a customary handshake. Unfortunately not everyone is in good terms with each other and hence not everyone does a handshake. Also, no one shakes hands with his/her spouse. One of these 10 people, Kevin, observes that everyone shook hands with different number of people. How many hands did Kevin shake?

Cheers,

[shivani]

BTW some more clues (for dumbos like me ) ( before MJ comes up with 5 different acceptable solutions)

[vivekpm]

Think about following points:

1. Number of handshakes observed by Kevin are unique.
2. Think about maximum number of handshakes a person can do under given conditions.
3. Given point 1 and 2, think about the possible number of handshakes observed by Kevin


Cheers,