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Math Help - help on some math questions???anyone?

  1. #1
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    Red face help on some math questions???anyone?

    I have some math questions:
    Reform the indicated operation. write in lowest terms.
    #8. 2 2/5 times 1 6/7?
    #10. 2 2/5 divide 6?
    #12. 1 1/6+4 3/5?
    #14. 50 1/4-32 2/3?
    #20. what is the least common denominator for 3/4 and 2/7?
    Does any one know these? it would be greatly appreciated. thank you.
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  2. #2
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    I don't KNOW any of those. They require a bit of calculation.

    Multiply mixed fractions by makign them improper fractions. Then multiply numerators and denominators. There may be reductions and simplifications along the way.

    #8. 2 2/5 times 1 6/7?

    2 2/5 = 12/5

    1 6/7 = 13/7

    (12/5)*(13/7) = 156/35

    Done. (Unless someone has a particular hatred for improper fractions)
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  3. #3
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    Quote Originally Posted by abb1327 View Post
    I have some math questions:
    Reform the indicated operation. write in lowest terms.
    #8. 2 2/5 times 1 6/7?
    #10. 2 2/5 divide 6?
    #12. 1 1/6+4 3/5?
    #14. 50 1/4-32 2/3?
    #20. what is the least common denominator for 3/4 and 2/7?
    Does any one know these? it would be greatly appreciated. thank you.
    #8  2\frac{2}{5} \cdot 1\frac{6}{7}

    Okay, let's get this straight: 2\frac{2}{5} is actually 2 + \frac{2}{5}. How can you combine fractions, do you know? Let me remind you that in order to add fraction, both fractions must have the same denominator ( \frac{Numerator}{Denominator}).
    \frac{2}{1} + \frac{2}{5} = \frac{2 \cdot 5}{1 \cdot 5} + \frac{2}{5} = \frac{10}{5} + \frac{2}{5} = \frac{12}{5}<br />
    Can you continue?

    #10
    One hint: to divide by a number is the same as multiply by the reciprocal of a number. For instance:

    12 6 = 2

    What is reciprocal of 6? \frac{1}{6}. What is reciprocal of 5 for instance? \frac{1}{5}.

    Let's check:

    12 \cdot \frac{1}{6}. = \frac{12}{6} = 2

    20. Use prime factorization

    I'm sure you can do them on your own now.
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  4. #4
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    Hello, abb1327!

    Preform the indicated operation. write in lowest terms.

    8.\;\;2\frac{2}{5} \times 1\frac{6}{7}

    With multiplication and division, we must convert to improper fractions.

    We have: . \begin{array}{ccc}2\frac{2}{5} &=& \frac{12}{5} \\ \\[-4mm]1\frac{6}{7} &=& \frac{13}{6} \end{array}

    Hence: . 2\frac{2}{5} \times 1\frac{6}{7} \:=\:\frac{12}{5}\cdot\frac{13}{6} \:=\:\frac{26}{5} \:=\:\boxed{5\frac{1}{5}}


    10.\;\;2\frac{2}{5} \div 6

    We have: . \begin{array}{ccc}2\frac{2}{5} &=&\frac{12}{5} \\ \\[-4mm] 6 &=& \frac{6}{1} \end{array}

    Hence: . 2\frac{2}{5} \div 6 \:=\:\frac{12}{5} \div \frac{6}{1} \:=\:\frac{12}{5} \times\frac{1}{6} \:=\:\boxed{\frac{2}{5}}



    12.\;\;1\frac{1}{6} + 4\frac{3}{5}

    With addition and subtraction, we can try to work with the whole numbers
    . . and the fractions separately.

    . . \begin{array}{ccc}& 1 & \frac{1}{6} \\ \\[-4mm]<br />
+ & 4 & \frac{3}{5} \\ \\[-4mm]\hline \\[-4mm]& 5 & {\color{red}?} \end{array}

    We added the whole number: . 1 + 4 \:=\:5

    Now add the fractions: . \frac{1}{6} + \frac{3}{5} \:=\:\frac{18}{30} + \frac{5}{30} \:=\:\frac{23}{30}

    Answer: . \boxed{5\frac{23}{30}}



    14.\;\;50\frac{1}{4} - 32\frac{2}{3}

    . . \begin{array}{ccc} & 50 & \frac{1}{4} \\ \\[-4mm] - &32 & \frac{2}{3} \\ \\[-4mm] \hline \\[-4mm] & 18 & {\color{red}?}<br />
 \end{array}

    But we find that: . \frac{1}{4} - \frac{2}{3} is negative . . . but this is not a problem!

    Subtract: . \frac{1}{4} - \frac{2}{3} \:=\:\frac{3}{12} - \frac{8}{12} \:=\:-\frac{5}{12}

    Hence, we have: . 18 - \frac{5}{12} \:=\:17 + 1 -\frac{5}{12} \;=\;17 + \frac{7}{12}

    Answer: . \boxed{17\frac{7}{12}}




    20. What is the least common denominator for \frac{3}{4} and \frac{2}{7} ?
    The denominators are 4 and 7.

    The LCD is: . 4\!\cdot\!7\:=\:\boxed{28}


    This is a rather silly problem, isn't it?
    We have supposedly completed nineteen problems already, with
    . . multiplication, division, addition and subtraction of fractions.

    And then they ask if we know to find a common denominator ??
    . . Well, duh!

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  5. #5
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    Soroban, 6 \neq 7. Please review the first problem.
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  6. #6
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    Smile what happened?

    wait what do you mean that 6 is not = to 7 where do u see that at?
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  7. #7
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    Quote Originally Posted by abb1327 View Post
    wait what do you mean that 6 is not = to 7 where do u see that at?
    1\frac67 = \frac{13}7, not \frac{13}6.
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