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Thread: find out the number.

  1. #1
    Expert Member
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    410

    find out the number.

    Consider the following triangular arrangement of numbers.
    1
    2 3
    4 5 6
    7 8 9 10
    11 12 13 14 15
    • • • • • •
    The middle number of the 51st row is?

    -- James.


  2. #2
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    410

    Re: find out the number. -- Answer

    It is obvious that line 'n' ends with the number n*(n+1)/2.

    ( line 2 ends with 2*3/2=3
    line 3 ends with 3*4/2=6 and
    line 4 ends with 4*5/2=10)

    Therefore line 50 will end with the number 50*51/2 =1,275
    middle number in the 51st row is the 26th number in the row.

    Hence Middle number in the 51st row is 1,275 +26 = 1,301.

    -- James.


  3. #3
    Junior Member
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    Jan 2007
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    1

    Re: find out the number.

    the middle no of 51 st row is 197


  4. #4
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    7

    Exclamation Re: find out the number.

    is it 1300


  5. #5
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    Oct 2005
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    383

    Re: find out the number.

    i think it is 1301!
    James ravid please verify this!

    bye

    :)
    NEVER SAY DIE.

  6. #6
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    249

    Re: find out the number.

    Yeah i too think the answer is 1301...

    Thanks
    Manoj


  7. #7
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    272

    Re: find out the number.

    and I confirm it wud b 1301


  8. #8
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    Sep 2006
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    477

    Re: find out the number.

    Please check this
    Re: find out the number. -- Answer
    It is obvious that line 'n' ends with the number n*(n+1)/2.

    ( line 2 ends with 2*3/2=3
    line 3 ends with 3*4/2=6 and
    line 4 ends with 4*5/2=10)

    Therefore line 50 will end with the number 50*51/2 =1,275
    middle number in the 51st row is the 26th number in the row.

    Hence Middle number in the 51st row is 1,275 +26 = 1,301.

    -- James.
    James had already given answer.
    (Second post in the thread)

    Cheers!
    Kalayama

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