Bueno, comenzando hacia atrás:
- $$ \ text {R} _1 = 10 + 15 + \ text {R} \ tag1 $$
- $$ \ text {R} _2 = \ frac {30 \ cdot \ text {R} _1} {30+ \ text {R} _1} \ tag2 $$
- $$ \ text {R} _3 = 32 + 25 + \ text {R} _2 \ tag3 $$
- $$ \ text {R} _4 = \ frac {60 \ cdot \ text {R} _3} {60+ \ text {R} _3} \ tag4 $$
- $$ \ text {R} _5 = \ text {R} _ {\ space \ text {in}} = 8 + 7 + \ text {R} _4 \ tag5 $$
Entonces, obtenemos:
$$ \ text {V} _ {\ space \ text {in}} = 250 = \ text {I} _ {\ space \ text {in}} \ cdot \ text {R} _ {\ space \ texto {en}} = $$
$$ \ text {I} _ {\ space \ text {in}} \ cdot \ left \ {8 + 7 + \ frac {60 \ cdot \ left (32 + 25 + \ frac {30 \ cdot \ left (10 +15+ \ text {R} \ right)} {30 + 10 + 15 + \ text {R}} \ right)} {60 + 32 + 25 + \ frac {30 \ cdot \ left (10 + 15 + \ text {R} \ right)} {30 + 10 + 15 + \ text {R}}} \ right \} = $$
$$ 225 \ cdot \ text {I} _ {\ space \ text {in}} \ cdot \ frac {505 + 11 \ cdot \ text {R}} {2395 + 49 \ cdot \ text {R}} \ tag6 $ $
Entonces, por ejemplo, cuando \ $ \ text {I} _ {\ space \ text {in}} = \ text {I} _ {\ space \ text {T}} = 5 \ space \ text {A} \ $, obtenemos:
$$ 250 = 225 \ cdot1 \ cdot \ frac {505 + 11 \ cdot \ text {R}} {2395 + 49 \ cdot \ text {R}} \ space \ Longleftrightarrow \ space \ text {R} = 245 \ tag7 $$