+0

0
510
4

Given $dc = 7$, $cb = 8$, $ab = \frac{1}{4}ad$, and $ed = \frac{4}{5}ad$, find $fc$. Express your answer as a decimal.

Jan 30, 2019

#1
+111357
+1

We have that

AD = DC + CB + AB

AD = 15 * (4/3)  =  20

So  ED = (4/5)AD = (4/5)(20) = 16

Note that CA = CB + AB = 8 + (1/4)AD  = 8 + (1/4)16  = 8 + 4 = 12

So....by similar triangles

16 / 20 = FC / 12

4 /5 = FC /12   multiply both sides by 12

12 * 4 /5  =  FC  =    48 / 5  =   9.6

Jan 30, 2019
#2
0

I dont think that is the right answer

Guest Jan 31, 2019
#3
0

Note that CA = CB + AB = 8 + 5  = 13[Cphill made a small typo here. CA should be 13 not 12.
So....by similar triangles
16 / 20 = FC / 13
4 /5 = FC /13   multiply both sides by 13
13 * 4 /5  =  FC  =    52 / 5  =   10.4

Jan 31, 2019
#4
+111357
0

Thanks, Guest!!

CPhill  Jan 31, 2019