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Math Help - need help with basic fraction problem

  1. #1
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    need help with basic fraction problem

    ok say i have this problem 38/64 + 72/109 = 136/173 .. how do i simplify that? and one last question.. how do i find the percentage of something.. like say if joe has 42$ and the bank account has 535$ in it how much percent money does he have on him compared to whats in his bank account? whats the equation to figure that out? 42 x .535? i dont get it.. thanks
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  2. #2
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    Quote Originally Posted by math_dummy View Post
    ok say i have this problem 38/64 + 72/109 = 136/173 .. how do i simplify that? and one last question.. how do i find the percentage of something.. like say if joe has 42$ and the bank account has 535$ in it how much percent money does he have on him compared to whats in his bank account? whats the equation to figure that out? 42 x .535? i dont get it.. thanks
    You can either use your calculator and number crunch or get a common denominator which would be 64x109. FYI, I do not get the LHS to equal the RHS, should there be an x term somewhere?

    The percentage of a in b is given by

    \frac{a}{b} \times 100\% which gives the answer as a percentage. In your case a=42 and b = 535
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  3. #3
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    Quote Originally Posted by e^(i*pi) View Post
    You can either use your calculator and number crunch or get a common denominator which would be 64x109. FYI, I do not get the LHS to equal the RHS, should there be an x term somewhere?

    The percentage of a in b is given by

    \frac{a}{b} \times 100\% which gives the answer as a percentage. In your case a=42 and b = 535
    so the percentage would be 7.850467289ectect..%? what is the normal way to round it off for college math classes? do teachers expect you to write down the whole long number or is 7.85% good enough? what would i put into a calculator to get the 64x109? also what is the LHS and RHS acronym mean? im a complete math noob, thanks
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  4. #4
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    Quote Originally Posted by math_dummy View Post
    so the percentage would be 7.850467289ectect..%? what is the normal way to round it off for college math classes? do teachers expect you to write down the whole long number or is 7.85% good enough? what would i put into a calculator to get the 64x109? also what is the LHS and RHS acronym mean? im a complete math noob, thanks
    Correct. Normally you'd do either 3 significant figures (7.85%), 2 decimal places (7.85%) or to the lowest level of accuracy in the question (7.9% because 42 is two significant figure). Which to use depends on your professor

    LHS = left hand side
    RHS = right hand side

    To get the fractions to have an equal denominator you'd have to multiply by the denominator of the other which seems a pointless question when most modern calculators have a fraction button. You can cancel 38/64 to 19/32 if you so wanted but I'd stick with a calculator
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  5. #5
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    Quote Originally Posted by e^(i*pi) View Post
    Correct. Normally you'd do either 3 significant figures (7.85%), 2 decimal places (7.85%) or to the lowest level of accuracy in the question (7.9% because 42 is two significant figure). Which to use depends on your professor

    LHS = left hand side
    RHS = right hand side

    To get the fractions to have an equal denominator you'd have to multiply by the denominator of the other which seems a pointless question when most modern calculators have a fraction button. You can cancel 38/64 to 19/32 if you so wanted but I'd stick with a calculator
    What does the button look like to get the common denominator? I have to know this for a college math placement test, i have this summer i want to study because i did terrible on the last test. Last time i dont think they allowed calc's.. so to do it without a calc then i would need to multiply the both denomitors? so for example

    12 over 39 plus 4 over 7, to get the common denominator i would multiply 39x7 equaling 273..? then how do i simplfy it from there? thanks
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  6. #6
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    Quote Originally Posted by math_dummy View Post
    What does the button look like to get the common denominator? I have to know this for a college math placement test, i have this summer i want to study because i did terrible on the last test. Last time i dont think they allowed calc's.. so to do it without a calc then i would need to multiply the both denomitors? so for example

    12 over 39 plus 4 over 7, to get the common denominator i would multiply 39x7 equaling 273..? then how do i simplfy it from there? thanks
    <br />
\frac{12}{39} + \frac{4}{7}

    You need to then multiply 12/39 by 7/7 and 4/7 by 39/39 (using the multiply button) to give:

    \frac{12 \times 7 + 4 \times 39}{7 \times 39} which may or may not cancel.
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  7. #7
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    What does the fraction button look like? is it only on scientific calc's?
    the "/" i always used to divide

    also what are the ( )'s used for? are those the equations you are suppose to do first?
    like say 2+(3x*4)-1=?
    Last edited by math_dummy; May 13th 2009 at 02:58 PM. Reason: added something
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  8. #8
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    Dividing is the same as the fraction. Calculators don't usually work with fractions, but in this question you have to evaluate the fraction as a decimal number for the percentages anyway. This question should be easy enough to solve by hand though.

    There's a rule to which operations get evaluated first in general, starting with the first first:

    powers, multiplication, division, roots, addition, substraction.

    So if you need to alter the evaluation order in any way, you can use brackets to make sure that the bracketed stuff happens before anything else. say: (1+x)^2 does 1 + x first, then does it times itself for the 2nd power.
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  9. #9
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    Lightbulb

    so 2 over 26 is the same as 2 divided by 26?

    or 3 over 54 is the same as 3 divided by 54?

    I think its starting to click, how do you post the equations on here to look so elegant, and what if the problem looks like this, (the most ( ) symbols mean it is the top one to caluclate first?

    1x + (25*5) - ((7y+13)) / (3y) = ?

    so the ((7y+13)) is the first equation to calculate, then what next.. go from left to right on the calculations useing the next set of ( )'s since the others were double (( ))'s?

    is it abnormal to see ((((( ))))))'s?

    thanks
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  10. #10
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    Hello math_dummy
    Quote Originally Posted by math_dummy View Post
    so 2 over 26 is the same as 2 divided by 26?

    or 3 over 54 is the same as 3 divided by 54?
    Exactly right!

    I think its starting to click, how do you post the equations on here to look so elegant, and what if the problem looks like this, (the most ( ) symbols mean it is the top one to caluclate first?

    1x + (25*5) - ((7y+13)) / (3y) = ?

    so the ((7y+13)) is the first equation to calculate, then what next.. go from left to right on the calculations useing the next set of ( )'s since the others were double (( ))'s?

    is it abnormal to see ((((( ))))))'s?

    thanks
    We use something called LaTeX. Here are a couple of places you can look. The first is on this web-site: LaTeX Help, and the second is a page on Wikibooks: LaTeX/Mathematics - Wikibooks.

    To start you off, and to answer your specific question, you can create brackets of different shapes and sizes.
    Here's where it is on the Wikibooks page: Brackets, braces and delimiters.

    So, you just type the expression you want, select the text and then press the \Sigma button on this editor's toolbar, and you'll find your text is surrounded by [tex]...[/tex] brackets. So to make \Big(\frac{(7y+13)}{3y}\Big), for instance, you'd type:

    \Big(\frac{(7y+13)}{3y}\Big)

    Select the text you've just typed, press \Sigma, and it would appear like this in the editor:

    [tex]\Big(\frac{(7y+13)}{3y}\Big)[/tex]

    and like this

    \Big(\frac{(7y+13)}{3y}\Big)

    in the Preview window.


    Grandad


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  11. #11
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    amazing..

    i will have to learn to grasp onto that new stuff, the dividing over whatever made sense when explained like that. Is there any secret math tricks that you can help share?

    I remember one is doing your nine times tables, you put down the finger of which is the number like nine times 4 put down your forth finger, = 36.. ok maybe im completely retarded at math.. but those little tricks and stuf helped me remember the math.. like the pac-man sign always eats the greatre number.. 33 > 13

    stuff like that makes it easy to remember.. do you have any good links or advice on other methods to make it easy to remember? thanks
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  12. #12
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    There really aren't any great math tricks when it comes to simplifying fractions like in question 1, you only have to remember that if the numbers on the bottom are the same you can then work with the numbers up top.

    So I'll give you an example with variables (so you can set in any number and it will work) and then a number example so you can compare the two.
    Lets say you have the problem;

    \frac {a}{b} + \frac {c}{d}

    Now the bottom isnt the same, but we can fix that by multiplying b and d (because by law b*d = d*b) But to do that you have to multiply the top as well, the reason is if you multiply any number by say \frac{7}{7} you are really multiplying by 1, which doesnt change the number.
    Written out it looks like;

    \frac {a}{b}*\frac{d}{d} + \frac {c}{d}*\frac {b}{b}

    So our new fractions looks like:

    \frac {ad}{bd} + \frac {bc}{db}

    Now that our bottom is the same we can combine them and work with the top;

    \frac {ad + bc}{db}

    Then as long as you know the numbers, you can add and now it is a simple fraction. Here is what the whole process would look like with numbers:

    \frac {38}{64} + \frac{72}{109}

    (To get common denominator we need to multiply)

    \frac {38}{64} * \frac {109}{109} + \frac {72}{109} * \frac {64}{64}

    \frac {4142}{6976} + \frac {4608}{6976}

    Some large numbers, but notice the bottom of our fraction is now the same, so we can combine and work with the top. (Note: since there is a + between the fractions we add the top numbers, if there was a - we would have to subtract!)

    \frac {4142 + 4608}{6976}

    So our final fraction is:

    \frac {8750}{6976}

    You can either then use this in a normal calculator to get a decimal answer (not exact) or reduce this fraction to it's lowest terms, or simply write this fraction as it is (all the same number, but professors generally like fractions reduced.)

    Also I noticed in your original exampe you had the answer as 136/173 which isn't correct, was there another part to this problem?

    Hope this helps!

    -Raez
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