
Algebra PreAlgebra and Basic Algebra Math Forum 
View Poll Results: Read the question below, and then answer this poll:  
A. 100%  0  0%  
B. 22.5%  0  0%  
C. 38.97%  0  0%  
D. 45%  5  100.00%  
E. 0%  0  0%  
F. 11.25%  0  0%  
G. 90%  0  0%  
Voters: 5. You may not vote on this poll 
 LinkBack  Thread Tools  Display Modes 
December 14th, 2006, 07:07 AM  #1 
Senior Member Joined: Dec 2006 Posts: 1,111 Thanks: 0  Crack the lock!
Suppose that I'm trying to break a typical 3roller bicycle lock with each roller having the numbers 09 on it, making 1000 possible combinations. Further suppose that I am trying to break the lock by a brute force decryption attack, such that I start with combination 000 and work to combination 999. Also, suppose that I can try out 1 combination every 3 seconds, such that it would take me 50 minutes to check all probabilities. What is the probability that I will crack the lock in only 22.5 minutes? ( I'll post the answer in a few days, even though I imagine a lot of you will be able to figure out what it is pretty quickly. ) 
December 14th, 2006, 11:46 AM  #2 
Senior Member Joined: Nov 2006 From: I'm a figment of my own imagination :? Posts: 848 Thanks: 0 
It seems obvious from the poll that people are having no trouble figuring this one out. It's hardly a college level question. I'm in high school, have taken a single halfcredit course in prob/stats and know the answer.

December 14th, 2006, 11:59 AM  #3 
Senior Member Joined: Dec 2006 Posts: 1,111 Thanks: 0 
True, and it occurred to me later that I should have posted it in the high school forum. I think I'll move it there. (If I can figure out how!)

December 15th, 2006, 06:29 PM  #4 
Senior Member Joined: Nov 2006 From: I'm a figment of my own imagination :? Posts: 848 Thanks: 0 
I don't think that you can move it to the high school section, but you can request that the moderator, i.e., Einar, move it there. Einar: to move a post, once you have it opened, click on the move post icon at the bottom of the screen.

December 16th, 2006, 03:48 AM  #5 
Senior Member Joined: Dec 2006 Posts: 1,111 Thanks: 0 
The answer to this question, as everyone (who voted) seemed to be able to figure out quite easily, was choice D, or 45 %. Since the lock could be positively broken (100% chance) in 50 minutes, then after 22.5 minutes (45% of 50 minutes), 45% of the possible combinations would have been run through, and naturally there would be a 45% chance of breaking the lock.

December 16th, 2006, 04:29 PM  #6 
Senior Member Joined: Nov 2006 From: I'm a figment of my own imagination :? Posts: 848 Thanks: 0 
Obviously, Einar has not taken my hint. Is he even still using My Math Forum?

December 17th, 2006, 05:21 AM  #7 
Senior Member Joined: Dec 2006 Posts: 1,111 Thanks: 0 
Not sure. His post number has been constant at 15 for a while, as I remember.

December 19th, 2006, 03:22 PM  #8 
Senior Member Joined: Nov 2006 From: I'm a figment of my own imagination :? Posts: 848 Thanks: 0 
It's a lot easier to just move a topic than to leave a note for the moderator and hope he finds it! 
December 20th, 2006, 04:44 AM  #9 
Senior Member Joined: Dec 2006 Posts: 1,111 Thanks: 0 
Thanks! 

Tags 
crack, lock 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Crack a Code  MrMoco  Number Theory  0  February 24th, 2012 04:49 PM 
The Magic Lock!  jon1  Algebra  3  December 12th, 2011 09:38 PM 
Hard nut to crack plzz help  agenten83  Number Theory  1  April 20th, 2010 12:20 PM 
Crack a code.  Sarmer  Number Theory  7  March 18th, 2008 01:52 PM 