Question

1st and 2nd question on detail
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Answer 1

1 Take Lcm of 20,30,60

Lcm is 60

Take parallel formula. It would be 3+2+1/60 that will be 6/60 ans will be 10

Answer 2

1. r1=20 ohm.
$r(2) =30ohm$
1/R=1/20 +1/30 + 1/60. 1/R=(3+2+1)/60. 1/R =6/60 =1/10. R=10 ohm.
$combined \: resistance = 10ohm$