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Mathematics 21 Online
OpenStudy (mary1999):

AB=15, BC=x, BD=16, AD=25

OpenStudy (mary1999):

OpenStudy (mathmate):

If the question is to find x, then use the theorem 1.33 from the book: Geometry Revisited by Coxeter and Greitzer. It says: "Each angle bisector of a triangle divides the opposite side into segments proportional in length to the adjacent sides." Visually, it is like the following: |dw:1464915588012:dw| Guess you can take it from here.

OpenStudy (mary1999):

i did that and it told me the answer was wrong

OpenStudy (mary1999):

ok now im confused

OpenStudy (mathmate):

What did you get for the answer? and please show your calculations.

OpenStudy (mary1999):

I did 15/25=x/16

OpenStudy (mathmate):

So far so good, go on!

OpenStudy (mary1999):

so i got 25x=240

OpenStudy (mary1999):

x=9.6

OpenStudy (mathmate):

Sorry, I misread the question exactly the same way you did. It says BC=x, BD=16 (not CD).

OpenStudy (mathmate):

Since BC+CD=BD=16 we have CD=16-BC=16-x The equation is then: \(\large \frac{15}{25}=\frac{x}{16-x}\) So you can cross multiply and solve for x.

OpenStudy (mary1999):

so 25x=240-x

OpenStudy (mathmate):

nope, you need to distribute when you multiply 15 by 16-x 15(16-x)=240=15x

OpenStudy (mary1999):

i got it!! th answer is 6!

OpenStudy (mathmate):

* 240-15x

OpenStudy (mary1999):

thank you

OpenStudy (mathmate):

You're welcome! :) Try to remember the handy formula, it will be useful for other problems.

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