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Math Help - find wrong term

  1. #1
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    find wrong term

    find the wrong term in the given series
    63,28,215,511
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  2. #2
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    Quote Originally Posted by hena View Post
    find the wrong term in the given series
    63,28,215,511
    How about 28 because it is the only even number?
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  3. #3
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    Hello,

    Quote Originally Posted by hena View Post
    find the wrong term in the given series
    63,28,215,511
    Well, there are many possibilities...

    - the numbers are odd, so 28 is the wrong term
    - the numbers are in an increasing order, so 28 is the wrong term
    - the sum of the numbers is <10, so 28 is the wrong term
    - the one I prefer : they are all multiples of 7, so 215 is the wrong term


    And another one :
    - I don't know what term to choose, and I don't want to bother, so \emptyset is the wrong term
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    Quote Originally Posted by hena View Post
    find the wrong term in the given series
    63,28,215,511
    Though I am pretty sure of my answer, I dont know why I am sure :P

    The odd one out is 28 because the rest all are 1 short of a power of 2
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  5. #5
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    Quote Originally Posted by Isomorphism View Post
    Though I am pretty sure of my answer, I dont know why I am sure :P

    The odd one out is 28 because the rest all are 1 short of a power of 2
    Well, ähemm - isn't there is a slight difference between 215 and 255
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  6. #6
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    Quote Originally Posted by earboth View Post
    Well, ähemm - isn't there is a slight difference between 215 and 255
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  7. #7
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    Hello, hena!

    Find the wrong term in the given sequence: 63, 28, 215, 511
    Think cubes . . . 4^3 = 64,\quad 6^3 = 216,\quad 8^3 = 512


    We have: . \begin{array}{cccc}<br />
63 & 28 & 215 & 511 \\<br />
\downarrow & \downarrow & \downarrow & \downarrow \\<br />
4^3-1 & \quad{\color{red}?}\quad & 6^3-1 & 8^3-1 \end{array}

    The terms are of the form: n^3-1
    . . except 28, which is 3^3 {\color{red}+} 1 . . . and is in the wrong position.

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  8. #8
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    Quote Originally Posted by neha1 View Post
    find the wrong term in the given series
    63,28,215,511
    There's no wrong term. Furthermore, a possible fifth term is 803. Followed by 978, 923, 525, -329, .......
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