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ab=240

cd=500

d-bc=455

ac=215.

then, d=?

Guest Feb 20, 2017
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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

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