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Math Help - Finding the value of X for two Supplementary Angles

  1. #1
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    Finding the value of X for two Supplementary Angles

    suppose angles A and B are supplementary angles. Also suppose the measure of angle A is (2x -30)*degrees* and the measure of angle B is (2/3X + 15)*degrees*.

    Find the value of X. give an exact decimal answer answer.





    ok what I did was take angle A + B = 180, and solve for the X value. I had to combine the two X values into one ... then isolate X on one side of the equal sign.

    my answer was X= 435/8 which in decimal form is 54.375.


    was this correct?
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  2. #2
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    You can quickly check your answer, by calculating A and B from X, and checking that A + B = 180.

    I think you must have made a small mistake since using your value for X, A + B = 130.
    Last edited by snowtea; January 7th 2011 at 02:10 PM.
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  3. #3
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    Quote Originally Posted by sharkfood4 View Post
    suppose angles A and B are supplementary angles. Also suppose the measure of angle A is (2x -30)*degrees* and the measure of angle B is (2/3X + 15)*degrees*.

    Find the value of X. give an exact decimal answer answer.





    ok what I did was take angle A + B = 180, and solve for the X value. I had to combine the two X values into one ... then isolate X on one side of the equal sign.

    my answer was X= 435/8 which in decimal form is 54.375.


    was this correct?
    A+B=180^o

    \displaystyle\ 2x-30^o+\frac{2x}{3}+15^o=180^o\Rightarrow\frac{6x}{3  }+\frac{2x}{3}-30^o+15^o=180^o

    \Rightarrow\displaystyle\frac{8x}{3}-15^o=180^o

    \displaystyle\Rightarrow\frac{8x}{3}=180^o+15^o

    but somehow you got 180^o-35^o
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