Results 1 to 6 of 6

Math Help - help please

  1. #1
    Junior Member
    Joined
    Apr 2008
    Posts
    73

    Question help please

    evaluate

    8 3/4 + 12.25-5 1/2
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Quote Originally Posted by BeBeMala View Post
    evaluate

    8 3/4 + 12.25-5 1/2
    Hello,

    Is it 8 \cdot \frac 34+12.25-5 \cdot \frac 12 ?

    8 \cdot \frac 34=6

    5 \cdot \frac 12=2.5

    Is it okay ?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Apr 2008
    Posts
    73

    Question sorry

    Quote Originally Posted by Moo View Post
    Hello,

    Is it 8 \cdot \frac 34+12.25-5 \cdot \frac 12 ?

    8 \cdot \frac 34=6

    5 \cdot \frac 12=2.5

    Is it okay ?

    but the choice are: a) 16.5 b)15.5 C)15.47 d)16
    Last edited by BeBeMala; May 6th 2008 at 02:10 PM. Reason: sorry wrong choices....
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Quote Originally Posted by BeBeMala View Post
    but the choice are: a) 16.5 b)15.5 C)15.47 d)16
    Are you sure you copied them well ? Or did you copy the text correctly ? oO
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Apr 2008
    Posts
    73

    Cool

    Quote Originally Posted by Moo View Post
    Are you sure you copied them well ? Or did you copy the text correctly ? oO
    yes they're are correct..thank you for ur help
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Smile

    Quote Originally Posted by BeBeMala View Post
    evaluate

    8 3/4 + 12.25-5 1/2
    Moo is right: you didn't state the problem clearly. From that choice of answers, I assume you mean 8 and 3/4, and 5 and 1/2, and not 8*(3/4) and 5*(1/2). You have to be careful about this sort of thing, because this unfortunate notation that we have for mixed fractions can be ambiguous. So, try to make sure people understand what you are asking.

    I will demonstrate how to evaluate this type of expression. Instead of solving your particular problem, I'll take you through another example, so that you can have the satisfaction of solving that one yourself.

    Consider this problem: Evaluate 2\frac56 + 4\frac12 - 3\frac49.

    Now, in this case the fractions next to the whole numbers are to be added, and not multiplied, so to avoid confusion I will rewrite this problem as:

    \left(2+\frac56\right) + \left(4+\frac12\right) - \left(3+\frac49\right)

    The first step is to convert these "mixed fractions" into "improper fractions" (but don't get hung up on the word "improper"--there's nothing wrong with having a numerator larger than a denominator). To do this conversion, transform the whole number into a fraction by multiplying and dividing it by the denominator of the fractional part and then combine the two together, like this:

    \left(2+\frac56\right) + \left(4+\frac12\right) - \left(3+\frac49\right)

    =\left(<br />
{\color{red}<br />
\frac{ {\color{black}2}\cdot6}{6} } + \frac56<br />
\right)<br />
+\left(<br />
{\color{red}<br />
\frac{ {\color{black}4}\cdot2}{2} } + \frac12<br />
\right)<br />
-\left(<br />
{\color{red}<br />
\frac{ {\color{black}3}\cdot9}{9} } + \frac49<br />
\right)<br />

    =\left(\frac{\color{red}12}{6}+\frac56\right) + \left(\frac{\color{red}8}{2}+\frac12\right) - \left(\frac{\color{red}27}{9}+\frac49\right)

    =\left(\frac{\color{red}12 + 5}{6}\right) + \left(\frac{\color{red}8 + 1}{2}\right) - \left(\frac{\color{red}27 + 4}{9}\right)

    =\left(\frac{\color{red}17}{6}\right) + \left(\frac{\color{red}9}{2}\right) - \left(\frac{\color{red}31}{9}\right)

    =\frac{17}6 + \frac92 - \frac{31}9

    Now, to add these fractions together, we need to find a common denominator. So, we find the least common multiple of 6, 2, and 9:

    6\cdot3 = 18

    2\cdot9 = 18

    9\cdot2 = 18

    Now, multiply the numerator and denominator of each fraction by the necessary amount to get a common denominator:

    \frac{17}6\cdot{\color{red}\frac33} + \frac92\cdot{\color{red}\frac99} - \frac{31}9\cdot{\color{red}\frac22}

    =\frac{17\color{red}\cdot3}{6\color{red}\cdot3} + \frac{9\color{red}\cdot9}{2\color{red}\cdot9} - \frac{31\color{red}\cdot2}{9\color{red}\cdot2}

    =\frac{51}{18} + \frac{81}{18} - \frac{62}{18}

    =\frac{\color{red}51 + 81 - 62}{18}

    =\frac{70}{18}

    Now simplify:

    \frac{70}{18} = \frac{35}9

    Did that help? Now you try!
    Last edited by Reckoner; May 6th 2008 at 04:34 PM. Reason: Sign error
    Follow Math Help Forum on Facebook and Google+


/mathhelpforum @mathhelpforum