1/R = 1/R1+ 1/R2 - Parallel Resistors

[xpack]

http://img42.imageshack.us/img42/1774/67916352.png [/URL]
1/R = 1/R1+ 1/R2 - Parallel Resistors
3. I thought it was 1048 but that was just because I thought 542*2 I really had no idea how to work this

 

[Mr.Green]

Resistors in Rectabgle 3 are in parallel with that in rectangle 2 and the parallel combination are in series with rectangle 1:

http://img34.imageshack.us/img34/1774/67916352.png


R_AB = [(R + R_L) // R] + R = R_L = 542

SO,

[(R + 542) * R / (R + R +542)] + R = 542