Fly

Written on 2:37 am by Vja Students

A fly sitting on one of the hours around the rim of a 12 hr clock took it into its primitive head ( i.e. decided ) to jump forward the same number of hours as the number of the hour it was first sitting on. It continued in this way with each jump moving the same number of hours until it was back where it had started. What are the chances that it visited all the hours before getting back to where it started ?




Ans: There are 4 chances out of 12 for the fly to sit.They are as follows

1 2 3 4 5 6 7 8 9 10 11 12 1

5 10 3 8 1 6 11 4 9 2 7 12 5

7 2 9 4 11 6 1 8 3 10 5 12 7

11 10 9 8 7 6 5 4 3 2 1 12 11

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2 Comments

  1. Unknown | 23 April 2008 at 2:00 am

    4 times:
    whn it iz on d following hrs
    1,5,7,11

    so probablity
    4/12 = 1/3

     
  2. Shekhar | 23 April 2008 at 8:47 pm

    2,3,4 and 6 are multiples of 12.and thier reflections are 10,9,8,and 6 respectively...fly sitting on these numbers will return to these without touching othrs.1 will surely cover all and hence its reflection 11.checking 5 ,it covers all and so does its replection i.e.7.
    so probability = 4/12=(1/3)

     

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