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CAT 2002 pblm

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  • subbu narayanaswamy
    dear friends this is a straight CAT 2002 pblm. 7^6n-6^6n, where n is an integer 0 is divisible by 1. 13 2. 127 3. 559 4. all of these answer given is 1. (i.e)
    Message 1 of 2 , Sep 2, 2003
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      dear friends
      this is a straight CAT 2002 pblm.

      7^6n-6^6n, where n is an integer >0 is divisible by

      1. 13
      2. 127
      3. 559
      4. all of these

      answer given is 1. (i.e) 13.

      my doubt is

      1,x^n - a^n is exactly divisible by (x+a) when n is even
      2,x^n - a^n is exactly divisible ny (x-a) irrespective of n

      by this funda 1, we get two answers
      1. 1st case (7^3)^2n-(6^3)^2n in this case it will be 7^3+6^3
      which is 559.
      2. 2nd case (7)^6n-(6)^6n in this case it will be 7+6 which is
      13.
      by funda 2, we get two answers
      1. 1st case (7^2)^3n-(6^2)^3n in this case it is x-a so it is
      13
      2. 2nd case (7^3)^2n-(6^3)^2n in this case it is x-a so 7*7*7 -
      6*6*6 which is 127

      so the answer should be all of these.

      but in the cat booklet they have taken into considetation only one
      aspect. so how to go about it??


      pblm 2

      a watch ticks 90 times in 95 seconds and another watch ticks 315
      times in 323 seconds. if both the watches are started together,
      how many times will they tick together in the first hour?

      ans is 101.
      kly help me out

      thanx and regards
      subbu

      ___________________________________________________
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    • Madan
      hi subbu well for the first problem, i have arrived at the same answer, i.e. all the options marked are correct. so perhaps there was a typing mistake in the
      Message 2 of 2 , Sep 13, 2003
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        hi subbu
                            well for the first problem, i have arrived at the same answer, i.e. all the options marked are correct. so perhaps there was a typing mistake in the cat booklet answers!!!
         
        for your second problem solution will be as follows:
        The first watch ticks once every 95/90 seconds, and the second ticks once every 323/315 seconds
        so they will tick together at the LCM of 95/90 and 315/323 i.e. 323/9 seconds
         
        Therefore, every hour or every 3600 seconds they will tick together 3600/ (323/9) times or 100 times ( ignoring the remainder 100/323). But since they were started together, we add one more to the number of times they tick together hence answer is 101
         
        Hope this would have helped
        regards
        madan
        subbu narayanaswamy <samarpan_subbu@...> wrote:
        dear friends
        this is a straight CAT 2002 pblm.

        7^6n-6^6n, where n is an integer >0 is divisible by

        1. 13
        2. 127
        3. 559
        4. all of these

        answer given is 1. (i.e) 13.

        my doubt is

        1,x^n - a^n is exactly divisible by (x+a) when n is even
        2,x^n - a^n is exactly divisible ny (x-a) irrespective of n

        by this funda 1, we get two answers
        1. 1st case (7^3)^2n-(6^3)^2n  in this case it will be 7^3+6^3
        which is 559.
        2. 2nd case (7)^6n-(6)^6n in this case it will be 7+6 which is
        13.
        by funda 2, we get two answers
        1. 1st case (7^2)^3n-(6^2)^3n  in this case it is x-a so it is
        13
        2. 2nd case (7^3)^2n-(6^3)^2n  in this case it is x-a so 7*7*7 -
        6*6*6 which is 127

        so the answer should be all of these.

        but in the cat booklet they have taken into considetation only one
        aspect. so how to go about it??


        pblm 2

        a watch ticks 90 times in 95 seconds and another watch ticks 315
        times in 323 seconds.  if both the watches are started together,
        how many times  will they tick together in the first hour?

        ans is 101.
        kly help me out

        thanx and regards
        subbu

        ___________________________________________________
        Medicine meets Marketing; Dr. Swati Weds Jayaram.
        Rediff Matchmaker strikes another interesting match !!
        Visit http://rediff.com/matchmaker?2




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