How to solve infinite ladder resistance if I’m first loop it has 3 R and in scnd it has 2 2R and 1 1R . And so on the symmetry is carried forming a GP

The simple aproach to solve this is , first solve for first ladder and ten second ladder , after that you will find they will form a GP . then apply the formula for infinite GP sum , The sum woul be equal to a/(1-r) , and you will get the desired ans, 

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Hope this help