Correct answer is option 'D'. Can you explain this answer?
*As ladder is infinitely long. so choose repeating element and mark it as Req /Rnet.*
here choose 10 ohm- 10 ohm as repeating.
then connect that resistance in series with the element which chosen as Repeating ie across CD. Now solve first series combination
then connect that solved resistance in parallel across AB solve parallel combination
R2=(100 10Req)/(20 Req)
and equate with Req as (Resistance across AB=Resistance across CD).
Req=(100 10Req)/(20 Req)
solve this for Req you get quadratic equation
By solving we get Req=6.18ohm
Now solve the series combination to get final euivalant Resistance
final Req = 5 6.18=11.18 ohms