A Trick for Solving Equations with FractionsDate: 11/12/95 at 23:24:18 From: Anonymous Subject: similar triangle Hi, I already wrote down the equation, and I solved for "y" but I can't figure out how to do "X". X+5 = 12+Y = 24 --- ---- -- X 12 18 To get "Y" I first go 12*24=288. Then I go 288 divided by 18 =16. 16 + 12 =28. (done) To find "X" I go.......... This is my guess. x+5 = 24 --- -- x 18 1) 24 multiply x to become 24x,and then 18(x+5). So now it's 18x +90 divided by 24x. Now after that I don't know what to do next. From Vic Date: 11/14/95 at 20:21:19 From: Doctor Jeremy Subject: Re: similar triangle One trick that comes in handy in cases like this is the fact that: a c - = - implies that ad = bc. b d You can get that by multiplying both sides by ad. In your case what that means is from x+5 24 --- = -- you get 18(x+5)=24x and you can probably take it from there. x 18 I've used the ad=bc trick so many times in so many cases I do it without thinking. It's one of those that is often not taught, but is really useful. -Doctor Jeremy, The Geometry Forum |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/dr.math/