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Math Help - Can you tell me if i solved this right

  1. #16
    MHF Contributor ebaines's Avatar
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    Re: Can you tell me if i solved this right

    This is simple manipulation of fractions.

     \frac {-1}{-3} + \frac 1 {-5} = \frac 1 3 + \frac {-1} 5

    To add these two fractions with different denominators you have to find the smallest common multiple of 3 and 5, which is 15. So:

     \frac 1 3 =  \frac {1 \times  5}{3 \times 5} = \frac 5 {15}

     \frac {-1} 5 = \frac {-1 \times 3}{5 \times 3 } = \frac {-3} {15}

    Hence:

      \frac 1 3 + \frac{-1 } 5  = \frac 5 {15} + \frac {-3} {15} = \frac 2 {15}
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  2. #17
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    Re: Can you tell me if i solved this right

    Quote Originally Posted by ebaines View Post
    This is simple manipulation of fractions.

     \frac {-1}{-3} + \frac 1 {-5} = \frac 1 3 + \frac {-1} 5

    To add these two fractions with different denominators you have to find the smallest common multiple of 3 and 5, which is 15. So:

     \frac 1 3 =  \frac {1 \times  5}{3 \times 5} = \frac 5 {15}

     \frac {-1} 5 = \frac {-1 \times 3}{5 \times 3 } = \frac {-3} {15}

    Hence:

      \frac 1 3 + \frac{-1 } 5  = \frac 5 {15} + \frac {-3} {15} = \frac 2 {15}
    *Face-palm* I don't how I missed that, I was over thinking and missing the basics..

    Thank you so much ebaines, your helping me out big time!
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  3. #18
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    Re: Can you tell me if i solved this right

    Quote Originally Posted by Urpes View Post
    All of that makes sense to me except for the  \frac 5 {15} + \frac {-3}{15}  part

    Where did those two come from?
    What number does 3 and 5 go into? 15. You cannot add fractions without common denominators.
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  4. #19
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    Re: Can you tell me if i solved this right

    Quote Originally Posted by Urpes View Post
    *Face-palm* I don't how I missed that, I was over thinking and missing the basics..

    Thank you so much ebaines, your helping me out big time!
    Oops. Did not see this post!
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