I have to admit I wasnt very smart. The key word here is minimum. But I was thinking in terms of power of 2 perhaps to find out the answer and trying to put in arbitrary numbers to find out the different permutations. After analysing it for 2 days, I concluded I wasnt meant to be a software engineer at Facebook.

So i went to google out the answers on internet – **the answer is 10**.

Initially I thought that a higher or lower number will impact the probability of guessing the number. I have no idea why but now thinking back, I feel stupid. Going by halving the range each time, it does not matter what the number is, as long as the range is halved, it has maximized the probability of getting the final answer within the shortest time.

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Playhouses King

said:No, actually the answer is one. Guess 2 and if the hint is lower then you have the answer.

clariice

said:In this perspective, you are right. I did consider this in fact. But logically I was assuming that they are choosing any random number – and in order to get to the right number within the shortest time, it’s assumed that we should have it to increase the probability of getting to the right answer. More of programming logic.

In fact, after I read your comment, I went to google out other comments and it states that the answer is 9 – taking into consideration that by the ninth try, we would have eliminated the other options.

Nash

said:Yeah, it really depends on the interpretation

1) Do you have to take the systematic probability route?

If so, the answer is 9 (or 10 if you count the final, certain answer)

Ha, and if you ignore this, then what happens if you guess spot on? The only hints you can get are ‘higher’ or ‘lower’. I would call this one guess, but the assumed test-giver wouldn’t be able to say anything to verify a correct guess…

hectoruno

said:When the test-giver can no longer say higher or lower you are verified.

clariice

said:You have a point. Probably the whole purpose of the question is for you to verify the question – test your logical thinking and your answer will demonstrate your analytical skill.

So if you can justify your answer with well-thought out of solution, they will most likely be impressed with your confidence and delivery 🙂

joey

said:i answered 10 after 10s of thinking (and yes, i calculate it based on assumption that it is to guess a random no). but playhouse’s answer of 2 is also logical, if word minimum is what the interviewer looking for..

Ben

said:Would the same then go for 1, by just guessing the right number?

wordcoaster

said:Yeah, I had the same thought. The minimum guesses could certainly be one. The person just has to be lucky. (But the question says nothing against that possibility.)

clariice

said:If we state the assumption before we give our guess –

That is given that we are all aware that the probability of getting it right on the first try is 0.001. We assume that the interviewee is able to get his answer right on the first try, then 1 is also acceptable.

In this case, we are only focusing on the key word minimum and we are assuming that we are all lucky in lottery.

Examining this question from all angle..we should actually accept either 1 or 10 with the corresponding assumptions and justification for each of the following.

I am very sure it will not be faulted as long as we are able to provide the proof for the answer.