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Math Help - Subtracting Mixed Fractions

  1. #1
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    Subtracting Mixed Fractions

    got this question and some others.
    i got 4and 1 third - 3 and 6 sevenths i need to know the answer and how to do it if you can help please post thanks.
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  2. #2
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    Quote Originally Posted by andyboy179 View Post
    got this question and some others.
    i got 4and 1 third - 3 and 6 sevenths i need to know the answer and how to do it if you can help please post thanks.
    Okay, I'll type as fast as I can!

    1) Change to "improper fractions" 4 is \frac{12}{3} because 12/3= 4. "4 and 1/3" is \frac{12}{3}+\frac{1}{3}= \frac{13}{3}. Similarly 3 is \frac{21}{7} because 21/7= 3. "3 and 6 sevenths" is \frac{21}{7}+ \frac{6}{7}= \frac{27}{6}.

    So "4 and 1/3 minus 3 and 6/7" is \frac{13}{3}- \frac{27}{7}. To add or subtract two fractions you need a "common denominator". Since 3 and 7 have no factors in common, we can just multiply the numerator and denominator of the first fraction by 7, \frac{7(13)}{7(3)}= \frac{91}{21}, and multiply the numerator and denominator of the second fraction by 3, \frac{3(27)}{3(7)}= \frac{81}{21}.

    Now the problem is \frac{91}{21}-\frac{81}{21} and we can simply subtract the numerators: \frac{10}{21}.
    Last edited by Jhevon; February 2nd 2009 at 09:47 PM. Reason: Fixed LaTeX
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  3. #3
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    thanks for the answer, but i don't really get what you have said in the post. is there any way you can explain the answer in an easierway, if so post again if not don't post. thnaks again for the help.
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  4. #4
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    Quote Originally Posted by andyboy179 View Post
    got this question and some others.
    i got 4and 1 third - 3 and 6 sevenths i need to know the answer and how to do it if you can help please post thanks.
    Hope this helps!

    4\frac{1}{3} = \frac{13}{3} = \frac{13}{3}\frac{7}{7} = \frac{91}{21}

    3\frac{6}{7} = \frac{27}{7} = \frac{27}{7}\frac{3}{3} = \frac{81}{21}

    4\frac{1}{3} - 3\frac{6}{7} = \frac{91}{21}-\frac{81}{21} = \frac{10}{21}

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  5. #5
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    thanks alot for your help
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  6. #6
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    Estimate first!

    Quote Originally Posted by andyboy179 View Post
    [snip]
    i got 4and 1 third - 3 and 6 sevenths i need to know the answer and how to do it if you can help please post thanks.
    So you have 1/3 more than 4 and 1/7th less than 4. The answer is 1/3 + 1/7.
    Last edited by mr fantastic; December 21st 2008 at 01:43 AM. Reason: Added the quote environment
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