There was a good job going in the office and the boss could not decide which of the three candidates should have it, each of them being worthy of it and all of them very bright indeed. So he set them a problem and the one who solved it would get the job. He showed them five discs, three black and two white and said: I am going to put a disc on the forehead of each of you. You will be able to see the others discs but not your own. There will be no talking. By pure deduction you will have to work out what colour disc you have, and the one who does so gets the job.? He withheld the two white discs and put a black one on each of them. After a time one of the men stepped forward and successfully claimed the job. How did he figure out that he had a black disc on?
Come up with your Logic then We will Discuss !
The intelligent guy (Rakhel) thinks that his Manager (Deepesh) is very intelligent. First of all Deepesh is not going to put the two white disks together on the heads of Pramod and Zakir or vice versa. Otherwise Rakhel will immediately make out that he has Black disk on his head.
ReplyDeleteNow Rakhel will discard one white disk. So the puzzle is narrowed to having 3 Black and 1 White disk. Rakhel is seeing that there are two black disks on Zakir's and Promod Lal Das's head. So he thinks if he would have white disk then Pramod or Zakir should have shouted that they have black disk. But Promod and Zakir are looking very serious. So they are confused as me. Rakhel has no doubt on intelligence of PLD and Zaks. So Rakhel comes forward and says: My Lord Deepesh, may I have permission to tell the answer. Lord Deepesh became very happy and given him permission to speak. My Lord I waited patiently for PLD and Zaks to speak up but both does not believe in these earthly matters of good job, gfs etc etc. PLD is thinking of completing the tutorial so that he can handover the completed tutorial at GH. Zaks is thinking of downloading a new application for Linux to play a particular movie type format. So I am the only suitable person, justified for this job. I am very much sure that my Lord will put only a black disk on my head.
Don’t mind,
Your Lord.
Hello My Lord !
ReplyDeleteIt's brilliant. But still i wonder why it's Rakhel why not pramod or Zakir, as the condition is same for all of them. Besides their priorities which you mentioned from your own.
Seriously if it's same for all the three then why one came up with the answer before the rest two.
This comment has been removed by the author.
ReplyDeleteBecause PLD and Zaks are not as smart as Rk. For the same priority case, one who speaks first, will win. :-)
ReplyDeleteI would like to think about it from a fresh angle.
Your Lord :-)
If you think that PLD and Zaks are not that intelligent then you can trust their confusion, because they can be confused by seeing two white also.
ReplyDeleteI think this question itself is flawed as situation is same for all 3 and all are equally intelligent.
ReplyDeleteThere would be confusion in mind if one see black+black or black+white
Hence, 3rd person cannot ensure his colour as he cannot ensure that other's are confused assuming that other are confused seeing black+black or black+white
Only way one can succeed if he assume that problem must tricky to same level for all of us. Hence, we all must have same colour.But this itself is a flawed assumption.
Hi Prachi,
ReplyDeleteI think this is a question to test the thinking process rather than the practicality of the solution. Saying that this problem can be modified slightly to have a solution, The interviewer can discretized the process by putting some time line, like he can say after every 5 minutes i will ask, and he will wait for 2 seconds and then he will give them chance to think for 5 minutes and the process will go on for 1hr.
So when he asks for the first time, no one will come up with any answer, as deepesh pointed out in his previous answer there will be the confusion of 3B or 2B+1W.
But next time when he asks the fastest reflex guy will come up with the answer.
The answer makes sense because the puzzle asks about how? not who? that means the event has already happened we just have to give our logic.
Even with your solution of equal opportunity for everyone is also raises the same question of why not anyone else from the other two, but this answer is also correct as the puzzle asks how?
It’s a very intelligently framed question; I will post another interesting puzzle on the same line this weekend. This one will be more convincing and specific.