Break the security

You want to get through a security door, where you have to enter 3 digits as password, where each digit can be any from 0 to 9. The checking mechanism is, however, defective, and so will let you in if any 2 of your digits match with the password's. e.g. if the password is 087 and you enter 057, then you will be let in. You don't have much time and hence want to make as few tries as possible. What is the minimum number of tries in which you can definitely enter, and what are they (you need not give explicitly, if you describe a pattern).

...give your answer with proof.

Replies

raj87verma88

Why do you wish to break through a "Security Door"?
Kaustubh Katdare

I knew a method of solving this type of problems. Will have to scratch my skull for this one. Hmm! :neutral:
ms_cs

Let me know the answer?
Yamini L

I think answer for this should be 50
Saandeep Sreerambatla

Have got two methods of solving and got answers as 50 once and 55 for the next method.

So waiting what the person asked will tell ..😎😎
arsh86

English-Scared
Have got two methods of solving and got answers as 50 once and 55 for the next method.

So waiting what the person asked will tell ..😎😎

can u explain both methods???????????
Differential

Is the digit matching positional?
I mean, if pasword is 087, then it won't accept 507. Tough 2 digsits are there, they are at diff positions. RIGHT?
Saandeep Sreerambatla

Differential
Is the digit matching positional?
I mean, if pasword is 087, then it won't accept 507. Tough 2 digsits are there, they are at diff positions. RIGHT?

Correct.
pwd=087 if you give 057 it is correct.
😎
Raviteja.g

yes, if it does not care about positions then the number of tries would be decreased to great extent.
otherwise it would be critical .
anyway waiting for the answer........
ms_cs

... I like these type of problems...I need to see these type of ...Send the link here or send the book name
Differential

I tried to solve this one and got the answer as 91. Am I correct or what?

😕
Raviteja.g

Differential,
can you give explanation
then we can analyze whether you are correct or went wrong anywhere
ok
Raviteja.g

I tried to solve this one
where is the explanation boss!
I think you guessed the answer .
Am I right Differential!!!?
Differential

Raviteja.g
where is the explanation boss!
I think you guessed the answer .
Am I right Differential!!!?
I have an explanation! I'm waiting to hear if my answer is right or wrong.
There is no point in telling the explanation if answer is wrong.
sarveshgupta

is the answer 100?
Saandeep Sreerambatla

The answer should be either 50 or 55
Digs

According to me the answe is 61...i found it out by using a simple mathematical technique..is it right??
RajdeepCE

The number is 99, if it concerns the position. Cause we have to guess 2 number & there are 99 possiblities.
But if the position is not concerned than the number of tries wilk be decreased. So as per my calculation the number of tries for this method is 55. The explanation for is that for each series e.g. 0-9, 10-19, 20-29,..., 90-99. The combination will decrease one for each series, cause the number is repeated already. That means series will be 0-9, 11-19, 22-29, 33-39,...,99. So the total number of tries will be 55.
Am I right? I am very keen to know the answer if I am wrong.
Differential

Looks like the one who asked the question and knows the real answer is away for long. Let's wait for him.

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Break the security

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