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Defective Clock


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4 replies to this topic

#1 BMAD

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Posted 14 July 2013 - 04:45 AM

BMAD has a defective clock in his room. The clock is digital, and some of the seven bars on its units digit are broken. A bar that works is on when it should be and off when it should be, whereas a broken bar is off regardless of the time.
 
a) BMAD enters his room and glances at his clock. He knows how many bars are broken but he doesn't know which ones they are. He immediately knows for sure what the time is.
b) BMAD enters his room and glances at his clock. He knows which bars are broken and immediately knows for sure what the time is.
c) BMAD enters his room and knows which bars are broken. He stares at his clock for 60 seconds. Now he knows for sure what time it is.
d) BMAD enters his room. He knows how many bars are broken but he doesn't know which ones they are. He stares at his clock for 60 seconds. Now he knows for sure what time it is.
 
In each of these four scenarios, what is the maximum number of broken bars, and which might it/they be?

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#2 gavinksong

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Posted 14 July 2013 - 09:52 AM

Spoiler for


Edited by gavinksong, 14 July 2013 - 09:54 AM.

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#3 TimeSpaceLightForce

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Posted 14 July 2013 - 07:26 PM

Spoiler for


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#4 TimeSpaceLightForce

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Posted 14 July 2013 - 08:06 PM

Spoiler for


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#5 gavinksong

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Posted 15 July 2013 - 07:59 AM

Spoiler for adding an explanation


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