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Are u good in math?

  1. Jan 24, 2005 #1
    Hi

    I just want to know in a clock, 12’O clock both needles (hour and minute) will coincide (one over the other)
    My question is exactly at what time both needles will coincide again after 12’o clock

    Good luck.
     
  2. jcsd
  3. Jan 24, 2005 #2
    13.05 :shy: ?
     
  4. Jan 24, 2005 #3
    movement of hourhand:
    hour hand moves 360 degree in 12 hours.
    one hour is 30 degree. or 60 minutes =30 degree movement
    6 minutes = 3 degrees
    one minute= .5 degrees.
    5 minutes =2.5 degrees

    minute hand moves 360 degrees in 60 minutes
    5 minutes = 30 degrees
    one minute =6 degrees
    at 1:05 the hour hand is at 32.5 degrees . minute hand is at 30 degrees
     
  5. Jan 24, 2005 #4

    krab

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    Let [itex]\theta_h[/itex] be the angle of the hour hand away from the 12, and [itex]\theta_m[/itex] be the angle of the minute hand away from the 12. Then I think you can see that
    [tex]12\,\theta_h=\theta_m+360^\circ n[/tex]
    where n is an integer. Now set [itex]\theta_m=\theta_h[/itex] and solve for each n. For example, the first coincidence is at [itex]\theta_{h,m}=360^\circ/11[/itex], or 1:05:27.2727...
     
  6. Jan 25, 2005 #5

    Tide

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    Yes, but can you do it with hour, minute and second hands all coinciding? :-)
     
  7. Jan 25, 2005 #6
    12:00
    this is the only answer.....
     
  8. Jan 26, 2005 #7

    Tide

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    Can you prove it? :-)
     
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