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This question is also based on similar triangles

 

 Oct 17, 2018
 #1
avatar+103148 
+1

ED  =  (2/3) (20)  =  40/3

 

ΔABF ~ EDF

AB / BF  = ED / DF

20 / BF  = (40/3) / DF

20 / (40/3)  = BF /DF

60/40 = BF /DF

3/2 = BF /DF

So...there are 5 equal parts to BD  and  BF  is 3 of them...so...

BF   = (3/5)BD

 

And because  FG is parallel to DC in triangle BDC...then...

 

FG / BF  = CD /BD

FG / (3/5)BD  = 20 / ( BD)

 

FG  = (3/5)BD * 20  / BD  =  (3/5) * 20   =  12

 

 

cool cool cool

 Oct 17, 2018
 #2
avatar+464 
+1

Thank you Chris

 Oct 17, 2018

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