+ 23

# Quizz time XIII Prime Password

Mr.Nero is the best black hat in dark web. one day he aim one of online payment. he has to penetrate 343 layer of security. in the last layer, he use brute force method to crack 8 digit integer only password. 😎 hah.... whoever built the system is dumb. the first digit appear 7 , a prime number. second digit is x, so 7x is also prime. third digit is y, so 7xy is prime too. and all digit is always prime. 😨 what the heck.... Question is What is the password ?

51 Answers

+ 6

73939133 I guess

+ 16

Why am I always late? ugh...

+ 15

@Cyrus
77777777 is not prime

+ 15

second digit is x
third digit is y
it must be different
71111111 has the same second and third digit.

+ 15

look guys you don't understand it
7x must prime
your is 75.

+ 15

@Nikolay Nachev Sir
Thank you very much
😄😄😄😄😄😄😄😄

+ 14

You right @Dennis
i got new winner today.

+ 14

7 is prime
73 is prime
739 is prime
7393 is prime
73939 is prime
and so on...

+ 13

@Hatsy Rei
Wow, that is nice effort.
How did you do it?
Can i get the code, please?

+ 13

And here is a JS solution... Take a look - it turned out nicely 😃
https://code.sololearn.com/W4NDtfmNFAj0/?ref=app

+ 12

@Kinshuk
i am also amateur in coding
but the lesson that i learn from many years in becoming a teacher is you have to outsmart the question.
some question is a trap like lollipop quizz
some are not telling the whole data (mostly physics, you have to remember many constant because some question are not include it)
some is nested question inside the question (like law or economics)
some question is insanely long to calculate
and yes, some question is designed to make you made a false conclusion.
that is the point of making quizz here.
if i explain everything about the question, then i am lecturing here. (i dont think Sololearn will allow me teach math/physics/economic/chemistry here).
PS. if you think this question is tricky, try to solve physics question. i have many, but i don't think if it is proper here.

+ 11

@Agus Mei I tried using a code, but the numbers were too big for me, so I had to go online for a big num calculator to get a 99 digit which stems from 2ⁿ. After that I went in search for the nearest prime using a prime checker (yet another one for big nums) by adding integers to the 99 digit non-prime. One appeared after 249.
I admit, it is a very stupid way... The only guide I had was to make sure that the number remains odd, and does not end with 5.

+ 9

75135137

+ 9

Ohh ....now thinking

+ 9

You mean 7x is prime and then 7xy is also prime...now lets think of a new no. next in order take it as z then 7xyz is also prime?

+ 9

@Agus Mei Regarding the next faulty quiz that you removed some time ago (99-digit prime), I found one:
136703170298938245273281389194851335334573089430825777276610662900622062449960995201469573563941113
which is (2^326) + (3*83)
I know this clearly doesn't satisfy the requirements that each digit is a prime, but at least I tried. :'

+ 9

Wow Hatsy do you really got that no. by yourself

+ 9

This is not done...
If x and y are not same, won't a normal person assume the same for the rest?
Sorry Dennis, I'm not a great mathematician, just an amateur coder trying to code...
You're great, keep it up...

+ 8

@Nikhil I had some trouble coming up with (n) for a clean 99 digit num resulting from 2ⁿ though, had to use calculators.

+ 8

@Dennis
Now how the hell can I think that the rule was for x and y only!!!
Agus Mei should be more specific in this!!!