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Math Help - what is Sum of five odd number?

  1. #1
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    what is Sum of five odd number?

    The question is:
    What is sum of five odd numbers
    a)Even
    b)divisible by three
    c)divisible by 5
    d)a prime number
    e)non of the above
    The answer is none of above.
    But i think the answer should be divisible by 5 because:
    sum of x,x+2,x+4,x+6,x+8 is 5x + 20 which is always divisible by 5. Could anyone tell me what i am doing wrong here?
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  2. #2
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    Re: what is Sum of five odd number?

    odd number=o

    if o+o=even
    o+o+o=odd
    continuing in this way

    the conclusion we get is
    sum of odd numbers, even number of times is even

    and

    sum of odd numbers, odd numbers of times is odd

    so that is the only information given in the question.

    can u proceed further now.
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  3. #3
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    Re: what is Sum of five odd number?

    Quote Originally Posted by MikeNoob View Post
    But i think the answer should be divisible by 5 because:
    sum of x,x+2,x+4,x+6,x+8 is 5x + 20 which is always divisible by 5. Could anyone tell me what i am doing wrong here?
    It never said that the odd numbers were consecutive. For example: 1 + 3 + 5 + 7 + 11 = 27 which is not divisible by 5.
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  4. #4
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    Re: what is Sum of five odd number?

    @Reckoner. Yeah never noticed that. Thanks for pointing it out.
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    Re: what is Sum of five odd number?

    Quote Originally Posted by MikeNoob View Post
    The question is:

    The answer is none of above.
    But i think the answer should be divisible by 5 because:
    sum of x,x+2,x+4,x+6,x+8 is 5x + 20 which is always divisible by 5. Could anyone tell me what i am doing wrong here?
    Who said they have to be consecutive?

    a) is obviously false, b), c) and d) are not necessarily true. So it's e) none of the above.
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  6. #6
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    Re: what is Sum of five odd number?

    I Think It is not working as you describe your answer.
    android apps source code
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  7. #7
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    Re: what is Sum of five odd number?

    1+3+5+7+9 = 25
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  8. #8
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    Re: what is Sum of five odd number?

    Let the 1st number be x, then sum of 5 odd number would be:x, x+1,x+3,x+5,x+7,x+9= 5x+25
    then x=25/5= 5.
    Therefore, answer would be option (c).
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