+0  
 
0
159
1
avatar

ab=240

cd=500

d-bc=455

ac=215.

then, d=?

Guest Feb 20, 2017
 #1
avatar+87293 
0

ab=240       →  b = 240/a     (1)

cd=500    →  d = 500/c →  500/ (215/a)  →  500a / 215 → 100a/43

d-bc=455

ac=215   (4)  → c = 215/a

then, d=?

 

Put (1), (2), (4)  into (3)

 

100a/43  - [ 240/a] * [ 215/a]  = 455      multiply hrough by  a^2

 

(100/43)a^3  - 240*215  = 455a^2

 

(100/43)a^3 -  455a^2 - 51600 = 0

 

100a^3 - 19565a^2 - 2218800 = 0    →   a ≈ 196.23

 

So....d =100a / 43 =  [100*196.23] / 43 ≈ 456.348

 

 

cool coolcool

CPhill  Feb 20, 2017

12 Online Users

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.